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 $223.37   13.344%   $253.1765   $253.18   $253.20   $253.20  
  Purchase #2 $196.68   4.230%   $204.9996   $205.00   $205.00   $205.00  
  Purchase #3 $66.38   11.266%   $73.8584   $73.86   $73.85   $73.90  
  Purchase #4 $218.62   9.182%   $238.6937   $238.69   $238.70   $238.70  
  Purchase #5 $221.61   9.282%   $242.1798   $242.18   $242.20   $242.20  
  Purchase #6 $62.27   4.586%   $65.1257   $65.13   $65.15   $65.10  
  Purchase #7 $89.49   5.578%   $94.4818   $94.48   $94.50   $94.50  
  7 purchase totals = $1,078.42       $1,172.5155   $1,172.52   $1,172.60   $1,172.60