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 $194.64   3.242%   $200.9502   $200.95   $200.95   $201.00  
  Purchase #2 $205.85   3.410%   $212.8695   $212.87   $212.85   $212.90  
  Purchase #3 $196.80   3.375%   $203.442   $203.44   $203.45   $203.40  
  Purchase #4 $75.72   9.309%   $82.7688   $82.77   $82.75   $82.80  
  Purchase #5 $129.98   11.391%   $144.786   $144.79   $144.80   $144.80  
  Purchase #6 $18.48   9.772%   $20.2859   $20.29   $20.30   $20.30  
  Purchase #7 $75.33   13.299%   $85.3481   $85.35   $85.35   $85.30  
  7 purchase totals = $896.80       $950.4505   $950.46   $950.45   $950.50