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 $56.96   11.141%   $63.3059   $63.31   $63.30   $63.30  
  Purchase #2 $211.44   6.459%   $225.0969   $225.10   $225.10   $225.10  
  Purchase #3 $192.74   8.814%   $209.7281   $209.73   $209.75   $209.70  
  Purchase #4 $67.36   8.332%   $72.9724   $72.97   $72.95   $73.00  
  Purchase #5 $69.81   7.754%   $75.2231   $75.22   $75.20   $75.20  
  Purchase #6 $54.40   10.728%   $60.236   $60.24   $60.25   $60.20  
  Purchase #7 $22.74   11.179%   $25.2821   $25.28   $25.30   $25.30  
  7 purchase totals = $675.45       $731.8445   $731.85   $731.85   $731.80