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 $92.92   3.255%   $95.9445   $95.94   $95.95   $95.90  
  Purchase #2 $99.50   5.469%   $104.9417   $104.94   $104.95   $104.90  
  Purchase #3 $98.58   6.473%   $104.9611   $104.96   $104.95   $105.00  
  Purchase #4 $98.47   9.581%   $107.9044   $107.90   $107.90   $107.90  
  Purchase #5 $119.93   5.675%   $126.736   $126.74   $126.75   $126.70  
  Purchase #6 $31.26   8.515%   $33.9218   $33.92   $33.90   $33.90  
  Purchase #7 $187.93   11.826%   $210.1546   $210.15   $210.15   $210.20  
  7 purchase totals = $728.59       $784.5641   $784.55   $784.55   $784.50