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 $59.32   9.499%   $64.9548   $64.95   $64.95   $65.00  
  Purchase #2 $205.85   6.370%   $218.9626   $218.96   $218.95   $219.00  
  Purchase #3 $24.39   5.433%   $25.7151   $25.72   $25.70   $25.70  
  Purchase #4 $234.66   5.514%   $247.5992   $247.60   $247.60   $247.60  
  Purchase #5 $195.28   4.844%   $204.7394   $204.74   $204.75   $204.70  
  Purchase #6 $194.70   8.158%   $210.5836   $210.58   $210.60   $210.60  
  Purchase #7 $145.86   9.654%   $159.9413   $159.94   $159.95   $159.90  
  7 purchase totals = $1,060.06       $1,132.4960   $1,132.49   $1,132.50   $1,132.50