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 $116.44   8.168%   $125.9508   $125.95   $125.95   $126.00  
  Purchase #2 $189.45   6.167%   $201.1334   $201.13   $201.15   $201.10  
  Purchase #3 $244.25   10.843%   $270.734   $270.73   $270.75   $270.70  
  Purchase #4 $40.87   9.478%   $44.7437   $44.74   $44.75   $44.70  
  Purchase #5 $186.96   11.847%   $209.1092   $209.11   $209.10   $209.10  
  Purchase #6 $131.67   7.510%   $141.5584   $141.56   $141.55   $141.60  
  Purchase #7 $64.99   9.471%   $71.1452   $71.15   $71.15   $71.10  
  7 purchase totals = $974.63       $1,064.3747   $1,064.37   $1,064.40   $1,064.30