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 $64.80   5.267%   $68.213   $68.21   $68.20   $68.20  
  Purchase #2 $196.61   9.202%   $214.7021   $214.70   $214.70   $214.70  
  Purchase #3 $13.50   4.841%   $14.1535   $14.15   $14.15   $14.20  
  Purchase #4 $185.84   10.625%   $205.5855   $205.59   $205.60   $205.60  
  Purchase #5 $87.35   7.228%   $93.6637   $93.66   $93.65   $93.70  
  Purchase #6 $91.60   6.409%   $97.4706   $97.47   $97.45   $97.50  
  Purchase #7 $183.48   10.644%   $203.0096   $203.01   $203.00   $203.00  
  7 purchase totals = $823.18       $896.7980   $896.79   $896.75   $896.90