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 $43.96   13.558%   $49.9201   $49.92   $49.90   $49.90  
  Purchase #2 $223.38   10.119%   $245.9838   $245.98   $246.00   $246.00  
  Purchase #3 $184.97   5.727%   $195.5632   $195.56   $195.55   $195.60  
  Purchase #4 $154.43   8.697%   $167.8608   $167.86   $167.85   $167.90  
  Purchase #5 $82.49   13.629%   $93.7326   $93.73   $93.75   $93.70  
  Purchase #6 $227.52   4.679%   $238.1657   $238.17   $238.15   $238.20  
  Purchase #7 $169.68   8.719%   $184.4744   $184.47   $184.45   $184.50  
  7 purchase totals = $1,086.43       $1,175.7006   $1,175.69   $1,175.65   $1,175.80