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 $174.63   5.539%   $184.3028   $184.30   $184.30   $184.30  
  Purchase #2 $89.59   4.588%   $93.7004   $93.70   $93.70   $93.70  
  Purchase #3 $118.66   5.707%   $125.4319   $125.43   $125.45   $125.40  
  Purchase #4 $99.93   9.353%   $109.2765   $109.28   $109.30   $109.30  
  Purchase #5 $96.36   5.360%   $101.5249   $101.52   $101.50   $101.50  
  Purchase #6 $246.42   6.590%   $262.6591   $262.66   $262.65   $262.70  
  Purchase #7 $171.47   4.287%   $178.8209   $178.82   $178.80   $178.80  
  7 purchase totals = $997.06       $1,055.7165   $1,055.71   $1,055.70   $1,055.70