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 $55.48   11.708%   $61.9756   $61.98   $62.00   $62.00  
  Purchase #2 $116.77   10.752%   $129.3251   $129.33   $129.35   $129.30  
  Purchase #3 $200.97   9.781%   $220.6269   $220.63   $220.65   $220.60  
  Purchase #4 $37.28   3.230%   $38.4841   $38.48   $38.50   $38.50  
  Purchase #5 $6.27   9.585%   $6.871   $6.87   $6.85   $6.90  
  Purchase #6 $44.41   10.336%   $49.0002   $49.00   $49.00   $49.00  
  Purchase #7 $204.53   13.322%   $231.7775   $231.78   $231.80   $231.80  
  7 purchase totals = $665.71       $738.0604   $738.07   $738.15   $738.10