Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $184.94   7.252%   $198.3518   $198.35   $198.35   $198.40  
  Purchase #2 $231.36   9.546%   $253.4456   $253.45   $253.45   $253.40  
  Purchase #3 $167.58   11.300%   $186.5165   $186.52   $186.50   $186.50  
  Purchase #4 $216.37   11.482%   $241.2136   $241.21   $241.20   $241.20  
  Purchase #5 $245.45   9.733%   $269.3396   $269.34   $269.35   $269.30  
  Purchase #6 $218.38   11.498%   $243.4893   $243.49   $243.50   $243.50  
  Purchase #7 $178.41   3.145%   $184.021   $184.02   $184.00   $184.00  
  7 purchase totals = $1,442.49       $1,576.3774   $1,576.38   $1,576.35   $1,576.30