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 $52.26   13.368%   $59.2461   $59.25   $59.25   $59.20  
  Purchase #2 $87.41   3.473%   $90.4457   $90.45   $90.45   $90.40  
  Purchase #3 $197.26   3.505%   $204.174   $204.17   $204.15   $204.20  
  Purchase #4 $232.30   8.402%   $251.8178   $251.82   $251.80   $251.80  
  Purchase #5 $169.92   4.389%   $177.3778   $177.38   $177.40   $177.40  
  Purchase #6 $185.94   6.174%   $197.4199   $197.42   $197.40   $197.40  
  Purchase #7 $69.56   7.740%   $74.9439   $74.94   $74.95   $74.90  
  7 purchase totals = $994.65       $1,055.4252   $1,055.43   $1,055.40   $1,055.30