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 $62.26   11.180%   $69.2207   $69.22   $69.20   $69.20  
  Purchase #2 $106.35   6.156%   $112.8969   $112.90   $112.90   $112.90  
  Purchase #3 $194.30   7.447%   $208.7695   $208.77   $208.75   $208.80  
  Purchase #4 $111.70   12.159%   $125.2816   $125.28   $125.30   $125.30  
  Purchase #5 $23.35   5.306%   $24.589   $24.59   $24.60   $24.60  
  Purchase #6 $181.95   7.452%   $195.5089   $195.51   $195.50   $195.50  
  Purchase #7 $145.48   13.814%   $165.5766   $165.58   $165.60   $165.60  
  7 purchase totals = $825.39       $901.8432   $901.85   $901.85   $901.90