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 $22.87   13.528%   $25.9639   $25.96   $25.95   $26.00  
  Purchase #2 $190.87   8.369%   $206.8439   $206.84   $206.85   $206.80  
  Purchase #3 $120.58   5.640%   $127.3807   $127.38   $127.40   $127.40  
  Purchase #4 $233.27   13.823%   $265.5149   $265.51   $265.50   $265.50  
  Purchase #5 $232.37   9.797%   $255.1353   $255.14   $255.15   $255.10  
  Purchase #6 $26.51   3.302%   $27.3854   $27.39   $27.40   $27.40  
  Purchase #7 $190.82   13.629%   $216.8269   $216.83   $216.85   $216.80  
  7 purchase totals = $1,017.29       $1,125.0510   $1,125.05   $1,125.10   $1,125.00