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 $173.83   13.424%   $197.1649   $197.16   $197.15   $197.20  
  Purchase #2 $218.98   8.386%   $237.3437   $237.34   $237.35   $237.30  
  Purchase #3 $149.43   5.469%   $157.6023   $157.60   $157.60   $157.60  
  Purchase #4 $229.95   5.183%   $241.8683   $241.87   $241.85   $241.90  
  Purchase #5 $118.93   5.842%   $125.8779   $125.88   $125.90   $125.90  
  Purchase #6 $85.92   13.734%   $97.7203   $97.72   $97.70   $97.70  
  Purchase #7 $25.44   11.191%   $28.287   $28.29   $28.30   $28.30  
  7 purchase totals = $1,002.48       $1,085.8644   $1,085.86   $1,085.85   $1,085.90