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 $191.73   6.552%   $204.2921   $204.29   $204.30   $204.30  
  Purchase #2 $236.54   11.147%   $262.9071   $262.91   $262.90   $262.90  
  Purchase #3 $108.52   12.290%   $121.8571   $121.86   $121.85   $121.90  
  Purchase #4 $53.92   4.412%   $56.299   $56.30   $56.30   $56.30  
  Purchase #5 $220.66   5.746%   $233.3391   $233.34   $233.35   $233.30  
  Purchase #6 $189.50   6.407%   $201.6413   $201.64   $201.65   $201.60  
  Purchase #7 $186.54   10.599%   $206.3114   $206.31   $206.30   $206.30  
  7 purchase totals = $1,187.41       $1,286.6471   $1,286.65   $1,286.65   $1,286.60