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 $84.41   9.204%   $92.1791   $92.18   $92.20   $92.20  
  Purchase #2 $207.65   5.771%   $219.6335   $219.63   $219.65   $219.60  
  Purchase #3 $85.86   11.719%   $95.9219   $95.92   $95.90   $95.90  
  Purchase #4 $235.84   13.784%   $268.3482   $268.35   $268.35   $268.30  
  Purchase #5 $53.47   11.237%   $59.4784   $59.48   $59.50   $59.50  
  Purchase #6 $221.41   10.388%   $244.4101   $244.41   $244.40   $244.40  
  Purchase #7 $163.38   7.733%   $176.0142   $176.01   $176.00   $176.00  
  7 purchase totals = $1,052.02       $1,155.9854   $1,155.98   $1,156.00   $1,155.90