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 $211.79   12.217%   $237.6644   $237.66   $237.65   $237.70  
  Purchase #2 $206.51   11.255%   $229.7527   $229.75   $229.75   $229.80  
  Purchase #3 $155.42   11.741%   $173.6679   $173.67   $173.65   $173.70  
  Purchase #4 $70.47   8.575%   $76.5128   $76.51   $76.50   $76.50  
  Purchase #5 $59.67   4.367%   $62.2758   $62.28   $62.30   $62.30  
  Purchase #6 $167.44   10.348%   $184.7667   $184.77   $184.75   $184.80  
  Purchase #7 $219.89   4.544%   $229.8818   $229.88   $229.90   $229.90  
  7 purchase totals = $1,091.19       $1,194.5221   $1,194.52   $1,194.50   $1,194.70