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 $22.43   13.830%   $25.5321   $25.53   $25.55   $25.50  
  Purchase #2 $48.92   10.869%   $54.2371   $54.24   $54.25   $54.20  
  Purchase #3 $108.35   3.868%   $112.541   $112.54   $112.55   $112.50  
  Purchase #4 $153.99   13.157%   $174.2505   $174.25   $174.25   $174.30  
  Purchase #5 $228.79   11.251%   $254.5312   $254.53   $254.55   $254.50  
  Purchase #6 $230.32   5.714%   $243.4805   $243.48   $243.50   $243.50  
  Purchase #7 $183.99   6.480%   $195.9126   $195.91   $195.90   $195.90  
  7 purchase totals = $976.79       $1,060.4850   $1,060.48   $1,060.55   $1,060.40