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 $86.28   8.479%   $93.5957   $93.60   $93.60   $93.60  
  Purchase #2 $162.83   8.490%   $176.6543   $176.65   $176.65   $176.70  
  Purchase #3 $187.66   8.402%   $203.4272   $203.43   $203.45   $203.40  
  Purchase #4 $97.71   3.591%   $101.2188   $101.22   $101.20   $101.20  
  Purchase #5 $194.53   5.714%   $205.6454   $205.65   $205.65   $205.60  
  Purchase #6 $169.92   9.705%   $186.4107   $186.41   $186.40   $186.40  
  Purchase #7 $174.60   8.816%   $189.9927   $189.99   $190.00   $190.00  
  7 purchase totals = $1,073.53       $1,156.9448   $1,156.95   $1,156.95   $1,156.90