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 $64.30   5.702%   $67.9664   $67.97   $67.95   $68.00  
  Purchase #2 $224.92   12.598%   $253.2554   $253.26   $253.25   $253.30  
  Purchase #3 $197.63   10.163%   $217.7151   $217.72   $217.70   $217.70  
  Purchase #4 $57.70   4.573%   $60.3386   $60.34   $60.35   $60.30  
  Purchase #5 $88.78   6.243%   $94.3225   $94.32   $94.30   $94.30  
  Purchase #6 $192.52   5.768%   $203.6246   $203.62   $203.60   $203.60  
  Purchase #7 $209.60   8.237%   $226.8648   $226.86   $226.85   $226.90  
  7 purchase totals = $1,035.45       $1,124.0874   $1,124.09   $1,124.00   $1,124.10