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 $196.26   8.368%   $212.683   $212.68   $212.70   $212.70  
  Purchase #2 $13.88   9.140%   $15.1486   $15.15   $15.15   $15.10  
  Purchase #3 $103.82   5.708%   $109.746   $109.75   $109.75   $109.70  
  Purchase #4 $93.88   13.867%   $106.8983   $106.90   $106.90   $106.90  
  Purchase #5 $213.82   8.726%   $232.4779   $232.48   $232.50   $232.50  
  Purchase #6 $247.79   3.531%   $256.5395   $256.54   $256.55   $256.50  
  Purchase #7 $144.73   10.408%   $159.7935   $159.79   $159.80   $159.80  
  7 purchase totals = $1,014.18       $1,093.2868   $1,093.29   $1,093.35   $1,093.20