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 $44.61   4.640%   $46.6799   $46.68   $46.70   $46.70  
  Purchase #2 $193.73   5.573%   $204.5266   $204.53   $204.55   $204.50  
  Purchase #3 $116.67   10.394%   $128.7967   $128.80   $128.80   $128.80  
  Purchase #4 $80.91   4.239%   $84.3398   $84.34   $84.35   $84.30  
  Purchase #5 $92.90   6.670%   $99.0964   $99.10   $99.10   $99.10  
  Purchase #6 $102.68   7.740%   $110.6274   $110.63   $110.65   $110.60  
  Purchase #7 $55.47   6.137%   $58.8742   $58.87   $58.85   $58.90  
  7 purchase totals = $686.97       $732.9410   $732.95   $733.00   $732.90