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 $106.25   11.604%   $118.5793   $118.58   $118.60   $118.60  
  Purchase #2 $203.64   5.860%   $215.5733   $215.57   $215.55   $215.60  
  Purchase #3 $104.82   11.749%   $117.1353   $117.14   $117.15   $117.10  
  Purchase #4 $240.84   9.282%   $263.1948   $263.19   $263.20   $263.20  
  Purchase #5 $7.53   3.827%   $7.8182   $7.82   $7.80   $7.80  
  Purchase #6 $56.96   13.115%   $64.4303   $64.43   $64.45   $64.40  
  Purchase #7 $168.39   4.294%   $175.6207   $175.62   $175.60   $175.60  
  7 purchase totals = $888.43       $962.3519   $962.35   $962.35   $962.30