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 $124.55   7.834%   $134.3072   $134.31   $134.30   $134.30  
  Purchase #2 $187.29   9.428%   $204.9477   $204.95   $204.95   $204.90  
  Purchase #3 $249.27   4.528%   $260.5569   $260.56   $260.55   $260.60  
  Purchase #4 $231.96   5.741%   $245.2768   $245.28   $245.30   $245.30  
  Purchase #5 $53.70   7.439%   $57.6947   $57.69   $57.70   $57.70  
  Purchase #6 $189.36   4.360%   $197.6161   $197.62   $197.60   $197.60  
  Purchase #7 $25.50   3.344%   $26.3527   $26.35   $26.35   $26.40  
  7 purchase totals = $1,061.63       $1,126.7521   $1,126.76   $1,126.75   $1,126.80