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 $87.63   10.704%   $97.0099   $97.01   $97.00   $97.00  
  Purchase #2 $175.27   10.870%   $194.3218   $194.32   $194.30   $194.30  
  Purchase #3 $128.73   12.345%   $144.6217   $144.62   $144.60   $144.60  
  Purchase #4 $124.27   6.490%   $132.3351   $132.34   $132.35   $132.30  
  Purchase #5 $249.39   13.336%   $282.6487   $282.65   $282.65   $282.60  
  Purchase #6 $24.98   5.729%   $26.4111   $26.41   $26.40   $26.40  
  Purchase #7 $131.34   8.393%   $142.3634   $142.36   $142.35   $142.40  
  7 purchase totals = $921.61       $1,019.7117   $1,019.71   $1,019.65   $1,019.60