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 $67.62   9.363%   $73.9513   $73.95   $73.95   $74.00  
  Purchase #2 $60.30   10.446%   $66.5989   $66.60   $66.60   $66.60  
  Purchase #3 $214.72   6.862%   $229.4541   $229.45   $229.45   $229.50  
  Purchase #4 $117.87   13.162%   $133.384   $133.38   $133.40   $133.40  
  Purchase #5 $16.78   13.752%   $19.0876   $19.09   $19.10   $19.10  
  Purchase #6 $133.50   11.104%   $148.3238   $148.32   $148.30   $148.30  
  Purchase #7 $181.62   12.654%   $204.6022   $204.60   $204.60   $204.60  
  7 purchase totals = $792.41       $875.4019   $875.39   $875.40   $875.50