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 $145.86   4.196%   $151.9803   $151.98   $152.00   $152.00  
  Purchase #2 $208.66   7.525%   $224.3617   $224.36   $224.35   $224.40  
  Purchase #3 $167.57   11.834%   $187.4002   $187.40   $187.40   $187.40  
  Purchase #4 $250.38   11.336%   $278.7631   $278.76   $278.75   $278.80  
  Purchase #5 $154.93   4.178%   $161.403   $161.40   $161.40   $161.40  
  Purchase #6 $16.97   13.353%   $19.236   $19.24   $19.25   $19.20  
  Purchase #7 $158.71   7.443%   $170.5228   $170.52   $170.50   $170.50  
  7 purchase totals = $1,103.08       $1,193.6671   $1,193.66   $1,193.65   $1,193.70