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 $43.73   9.138%   $47.726   $47.73   $47.75   $47.70  
  Purchase #2 $179.83   8.792%   $195.6407   $195.64   $195.65   $195.60  
  Purchase #3 $189.57   9.188%   $206.9877   $206.99   $207.00   $207.00  
  Purchase #4 $232.50   10.434%   $256.7591   $256.76   $256.75   $256.80  
  Purchase #5 $35.49   5.111%   $37.3039   $37.30   $37.30   $37.30  
  Purchase #6 $131.35   5.700%   $138.837   $138.84   $138.85   $138.80  
  Purchase #7 $169.54   9.450%   $185.5615   $185.56   $185.55   $185.60  
  7 purchase totals = $982.01       $1,068.8159   $1,068.82   $1,068.85   $1,068.80