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 $175.60   10.872%   $194.6912   $194.69   $194.70   $194.70  
  Purchase #2 $206.32   11.243%   $229.5166   $229.52   $229.50   $229.50  
  Purchase #3 $197.52   3.618%   $204.6663   $204.67   $204.65   $204.70  
  Purchase #4 $54.48   7.315%   $58.4652   $58.47   $58.45   $58.50  
  Purchase #5 $234.43   6.495%   $249.6562   $249.66   $249.65   $249.70  
  Purchase #6 $107.73   5.571%   $113.7316   $113.73   $113.75   $113.70  
  Purchase #7 $249.35   13.490%   $282.9873   $282.99   $283.00   $283.00  
  7 purchase totals = $1,225.43       $1,333.7144   $1,333.73   $1,333.70   $1,333.80