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 $161.79   8.627%   $175.7476   $175.75   $175.75   $175.70  
  Purchase #2 $54.89   9.235%   $59.9591   $59.96   $59.95   $60.00  
  Purchase #3 $240.38   7.673%   $258.8244   $258.82   $258.80   $258.80  
  Purchase #4 $48.36   12.437%   $54.3745   $54.37   $54.35   $54.40  
  Purchase #5 $77.84   7.279%   $83.506   $83.51   $83.50   $83.50  
  Purchase #6 $194.76   12.873%   $219.8315   $219.83   $219.85   $219.80  
  Purchase #7 $15.86   8.287%   $17.1743   $17.17   $17.15   $17.20  
  7 purchase totals = $793.88       $869.4174   $869.41   $869.35   $869.40