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 $43.33   5.612%   $45.7617   $45.76   $45.75   $45.80  
  Purchase #2 $174.29   3.454%   $180.31   $180.31   $180.30   $180.30  
  Purchase #3 $104.83   9.464%   $114.7511   $114.75   $114.75   $114.80  
  Purchase #4 $93.35   3.500%   $96.6173   $96.62   $96.60   $96.60  
  Purchase #5 $71.25   6.269%   $75.7167   $75.72   $75.70   $75.70  
  Purchase #6 $118.29   5.655%   $124.9793   $124.98   $125.00   $125.00  
  Purchase #7 $97.45   10.744%   $107.92   $107.92   $107.90   $107.90  
  7 purchase totals = $702.79       $746.0561   $746.06   $746.00   $746.10