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 $54.46   13.777%   $61.963   $61.96   $61.95   $62.00  
  Purchase #2 $233.80   8.832%   $254.4492   $254.45   $254.45   $254.40  
  Purchase #3 $39.53   5.169%   $41.5733   $41.57   $41.55   $41.60  
  Purchase #4 $6.84   3.165%   $7.0565   $7.06   $7.05   $7.10  
  Purchase #5 $150.49   5.743%   $159.1326   $159.13   $159.15   $159.10  
  Purchase #6 $125.72   4.738%   $131.6766   $131.68   $131.70   $131.70  
  Purchase #7 $54.31   7.685%   $58.4837   $58.48   $58.50   $58.50  
  7 purchase totals = $665.15       $714.3349   $714.33   $714.35   $714.40