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 $84.64   11.839%   $94.6605   $94.66   $94.65   $94.70  
  Purchase #2 $134.64   10.428%   $148.6803   $148.68   $148.70   $148.70  
  Purchase #3 $143.43   10.163%   $158.0068   $158.01   $158.00   $158.00  
  Purchase #4 $245.96   12.482%   $276.6607   $276.66   $276.65   $276.70  
  Purchase #5 $59.69   4.834%   $62.5754   $62.58   $62.60   $62.60  
  Purchase #6 $203.38   11.374%   $226.5124   $226.51   $226.50   $226.50  
  Purchase #7 $102.54   6.205%   $108.9026   $108.90   $108.90   $108.90  
  7 purchase totals = $974.28       $1,075.9987   $1,076.00   $1,076.00   $1,076.10