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 $118.44   6.702%   $126.3778   $126.38   $126.40   $126.40  
  Purchase #2 $160.48   10.731%   $177.7011   $177.70   $177.70   $177.70  
  Purchase #3 $248.31   9.752%   $272.5252   $272.53   $272.55   $272.50  
  Purchase #4 $113.73   3.178%   $117.3443   $117.34   $117.35   $117.30  
  Purchase #5 $173.41   13.650%   $197.0805   $197.08   $197.10   $197.10  
  Purchase #6 $102.72   13.223%   $116.3027   $116.30   $116.30   $116.30  
  Purchase #7 $58.75   7.644%   $63.2409   $63.24   $63.25   $63.20  
  7 purchase totals = $975.84       $1,070.5725   $1,070.57   $1,070.65   $1,070.50