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 $69.46   6.550%   $74.0096   $74.01   $74.00   $74.00  
  Purchase #2 $214.91   9.322%   $234.9439   $234.94   $234.95   $234.90  
  Purchase #3 $208.33   5.774%   $220.359   $220.36   $220.35   $220.40  
  Purchase #4 $13.37   10.313%   $14.7488   $14.75   $14.75   $14.70  
  Purchase #5 $141.39   5.828%   $149.6302   $149.63   $149.65   $149.60  
  Purchase #6 $217.33   6.579%   $231.6281   $231.63   $231.65   $231.60  
  Purchase #7 $177.90   7.867%   $191.8954   $191.90   $191.90   $191.90  
  7 purchase totals = $1,042.69       $1,117.2150   $1,117.22   $1,117.25   $1,117.10