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 $169.27   3.224%   $174.7273   $174.73   $174.75   $174.70  
  Purchase #2 $226.86   11.746%   $253.507   $253.51   $253.50   $253.50  
  Purchase #3 $245.54   12.538%   $276.3258   $276.33   $276.35   $276.30  
  Purchase #4 $26.70   9.590%   $29.2605   $29.26   $29.25   $29.30  
  Purchase #5 $111.33   4.606%   $116.4579   $116.46   $116.45   $116.50  
  Purchase #6 $121.93   12.623%   $137.3212   $137.32   $137.30   $137.30  
  Purchase #7 $219.29   13.537%   $248.9753   $248.98   $249.00   $249.00  
  7 purchase totals = $1,120.92       $1,236.5750   $1,236.59   $1,236.60   $1,236.60