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 $233.82   12.221%   $262.3951   $262.40   $262.40   $262.40  
  Purchase #2 $200.67   4.797%   $210.2961   $210.30   $210.30   $210.30  
  Purchase #3 $196.92   4.650%   $206.0768   $206.08   $206.10   $206.10  
  Purchase #4 $83.44   4.536%   $87.2248   $87.22   $87.20   $87.20  
  Purchase #5 $239.67   12.832%   $270.4245   $270.42   $270.40   $270.40  
  Purchase #6 $169.34   8.176%   $183.1852   $183.19   $183.20   $183.20  
  Purchase #7 $168.74   13.761%   $191.9603   $191.96   $191.95   $192.00  
  7 purchase totals = $1,292.60       $1,411.5628   $1,411.57   $1,411.55   $1,411.60