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 $24.51   5.479%   $25.8529   $25.85   $25.85   $25.90  
  Purchase #2 $29.36   4.763%   $30.7584   $30.76   $30.75   $30.80  
  Purchase #3 $177.44   11.422%   $197.7072   $197.71   $197.70   $197.70  
  Purchase #4 $158.74   6.668%   $169.3248   $169.32   $169.30   $169.30  
  Purchase #5 $77.74   11.871%   $86.9685   $86.97   $86.95   $87.00  
  Purchase #6 $244.29   4.841%   $256.1161   $256.12   $256.10   $256.10  
  Purchase #7 $241.88   11.167%   $268.8907   $268.89   $268.90   $268.90  
  7 purchase totals = $953.96       $1,035.6186   $1,035.62   $1,035.55   $1,035.70