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 $92.94   3.668%   $96.349   $96.35   $96.35   $96.30  
  Purchase #2 $40.52   12.376%   $45.5348   $45.53   $45.55   $45.50  
  Purchase #3 $69.44   8.219%   $75.1473   $75.15   $75.15   $75.10  
  Purchase #4 $133.90   4.455%   $139.8652   $139.87   $139.85   $139.90  
  Purchase #5 $207.72   9.349%   $227.1397   $227.14   $227.15   $227.10  
  Purchase #6 $234.74   7.124%   $251.4629   $251.46   $251.45   $251.50  
  Purchase #7 $21.48   8.412%   $23.2869   $23.29   $23.30   $23.30  
  7 purchase totals = $800.74       $858.7858   $858.79   $858.80   $858.70