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 $88.31   11.330%   $98.3155   $98.32   $98.30   $98.30  
  Purchase #2 $25.95   8.679%   $28.2022   $28.20   $28.20   $28.20  
  Purchase #3 $212.37   4.519%   $221.967   $221.97   $221.95   $222.00  
  Purchase #4 $145.60   4.208%   $151.7268   $151.73   $151.75   $151.70  
  Purchase #5 $187.61   3.610%   $194.3827   $194.38   $194.40   $194.40  
  Purchase #6 $157.28   3.644%   $163.0113   $163.01   $163.00   $163.00  
  Purchase #7 $190.72   11.153%   $211.991   $211.99   $212.00   $212.00  
  7 purchase totals = $1,007.84       $1,069.5965   $1,069.60   $1,069.60   $1,069.60