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 $174.34   11.332%   $194.0962   $194.10   $194.10   $194.10  
  Purchase #2 $175.81   10.647%   $194.5285   $194.53   $194.55   $194.50  
  Purchase #3 $94.90   13.344%   $107.5635   $107.56   $107.55   $107.60  
  Purchase #4 $101.71   6.720%   $108.5449   $108.54   $108.55   $108.50  
  Purchase #5 $30.87   6.527%   $32.8849   $32.88   $32.90   $32.90  
  Purchase #6 $182.81   11.342%   $203.5443   $203.54   $203.55   $203.50  
  Purchase #7 $219.69   3.366%   $227.0848   $227.08   $227.10   $227.10  
  7 purchase totals = $980.13       $1,068.2471   $1,068.23   $1,068.30   $1,068.20