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 $118.87   5.688%   $125.6313   $125.63   $125.65   $125.60  
  Purchase #2 $34.67   9.134%   $37.8368   $37.84   $37.85   $37.80  
  Purchase #3 $107.35   4.332%   $112.0004   $112.00   $112.00   $112.00  
  Purchase #4 $111.31   4.689%   $116.5293   $116.53   $116.55   $116.50  
  Purchase #5 $65.59   12.671%   $73.9009   $73.90   $73.90   $73.90  
  Purchase #6 $102.54   13.852%   $116.7438   $116.74   $116.75   $116.70  
  Purchase #7 $33.82   3.809%   $35.1082   $35.11   $35.10   $35.10  
  7 purchase totals = $574.15       $617.7507   $617.75   $617.80   $617.60