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 $64.74   5.363%   $68.212   $68.21   $68.20   $68.20  
  Purchase #2 $125.97   7.505%   $135.424   $135.42   $135.40   $135.40  
  Purchase #3 $180.43   12.340%   $202.6951   $202.70   $202.70   $202.70  
  Purchase #4 $173.77   5.664%   $183.6123   $183.61   $183.60   $183.60  
  Purchase #5 $140.50   13.237%   $159.098   $159.10   $159.10   $159.10  
  Purchase #6 $238.40   6.325%   $253.4788   $253.48   $253.50   $253.50  
  Purchase #7 $67.63   9.132%   $73.806   $73.81   $73.80   $73.80  
  7 purchase totals = $991.44       $1,076.3262   $1,076.33   $1,076.30   $1,076.30