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 $61.44   10.703%   $68.0159   $68.02   $68.00   $68.00  
  Purchase #2 $96.45   6.312%   $102.5379   $102.54   $102.55   $102.50  
  Purchase #3 $210.59   10.202%   $232.0744   $232.07   $232.05   $232.10  
  Purchase #4 $208.94   12.407%   $234.8632   $234.86   $234.85   $234.90  
  Purchase #5 $144.80   5.285%   $152.4527   $152.45   $152.45   $152.50  
  Purchase #6 $232.30   4.740%   $243.311   $243.31   $243.30   $243.30  
  Purchase #7 $106.83   8.756%   $116.184   $116.18   $116.20   $116.20  
  7 purchase totals = $1,061.35       $1,149.4391   $1,149.43   $1,149.40   $1,149.50