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 $87.87   5.777%   $92.9462   $92.95   $92.95   $92.90  
  Purchase #2 $220.34   10.494%   $243.4625   $243.46   $243.45   $243.50  
  Purchase #3 $217.98   13.398%   $247.185   $247.19   $247.20   $247.20  
  Purchase #4 $5.92   11.187%   $6.5823   $6.58   $6.60   $6.60  
  Purchase #5 $242.52   4.620%   $253.7244   $253.72   $253.70   $253.70  
  Purchase #6 $173.95   12.599%   $195.866   $195.87   $195.85   $195.90  
  Purchase #7 $202.79   7.262%   $217.5166   $217.52   $217.50   $217.50  
  7 purchase totals = $1,151.37       $1,257.2830   $1,257.29   $1,257.25   $1,257.30