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 $201.37   7.568%   $216.6097   $216.61   $216.60   $216.60  
  Purchase #2 $68.96   11.198%   $76.6821   $76.68   $76.70   $76.70  
  Purchase #3 $12.63   3.234%   $13.0385   $13.04   $13.05   $13.00  
  Purchase #4 $29.94   6.108%   $31.7687   $31.77   $31.75   $31.80  
  Purchase #5 $210.35   3.311%   $217.3147   $217.31   $217.30   $217.30  
  Purchase #6 $184.59   5.213%   $194.2127   $194.21   $194.20   $194.20  
  Purchase #7 $166.83   7.106%   $178.6849   $178.68   $178.70   $178.70  
  7 purchase totals = $874.67       $928.3113   $928.30   $928.30   $928.30