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 $141.68   4.426%   $147.9508   $147.95   $147.95   $148.00  
  Purchase #2 $34.65   4.538%   $36.2224   $36.22   $36.20   $36.20  
  Purchase #3 $97.91   12.675%   $110.3201   $110.32   $110.30   $110.30  
  Purchase #4 $164.52   3.534%   $170.3341   $170.33   $170.35   $170.30  
  Purchase #5 $200.94   12.836%   $226.7327   $226.73   $226.75   $226.70  
  Purchase #6 $161.40   12.764%   $182.0011   $182.00   $182.00   $182.00  
  Purchase #7 $150.48   9.472%   $164.7335   $164.73   $164.75   $164.70  
  7 purchase totals = $951.58       $1,038.2947   $1,038.28   $1,038.30   $1,038.20