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 $209.46   8.246%   $226.7321   $226.73   $226.75   $226.70  
  Purchase #2 $90.59   10.605%   $100.1971   $100.20   $100.20   $100.20  
  Purchase #3 $12.80   9.527%   $14.0195   $14.02   $14.00   $14.00  
  Purchase #4 $16.54   7.605%   $17.7979   $17.80   $17.80   $17.80  
  Purchase #5 $95.71   9.671%   $104.9661   $104.97   $104.95   $105.00  
  Purchase #6 $118.37   11.751%   $132.2797   $132.28   $132.30   $132.30  
  Purchase #7 $156.83   5.432%   $165.349   $165.35   $165.35   $165.30  
  7 purchase totals = $700.30       $761.3414   $761.35   $761.35   $761.30