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 $195.38   5.692%   $206.501   $206.50   $206.50   $206.50  
  Purchase #2 $66.46   3.675%   $68.9024   $68.90   $68.90   $68.90  
  Purchase #3 $7.52   10.669%   $8.3223   $8.32   $8.30   $8.30  
  Purchase #4 $35.72   6.656%   $38.0975   $38.10   $38.10   $38.10  
  Purchase #5 $116.51   7.753%   $125.543   $125.54   $125.55   $125.50  
  Purchase #6 $231.84   7.840%   $250.0163   $250.02   $250.00   $250.00  
  Purchase #7 $194.30   10.196%   $214.1108   $214.11   $214.10   $214.10  
  7 purchase totals = $847.73       $911.4933   $911.49   $911.45   $911.40