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 $207.81   8.361%   $225.185   $225.19   $225.20   $225.20  
  Purchase #2 $249.96   7.603%   $268.9645   $268.96   $268.95   $269.00  
  Purchase #3 $35.88   5.248%   $37.763   $37.76   $37.75   $37.80  
  Purchase #4 $161.26   11.789%   $180.2709   $180.27   $180.25   $180.30  
  Purchase #5 $62.67   11.698%   $70.0011   $70.00   $70.00   $70.00  
  Purchase #6 $169.44   9.822%   $186.0824   $186.08   $186.10   $186.10  
  Purchase #7 $180.28   7.755%   $194.2607   $194.26   $194.25   $194.30  
  7 purchase totals = $1,067.30       $1,162.5276   $1,162.52   $1,162.50   $1,162.70