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 $67.77   7.344%   $72.747   $72.75   $72.75   $72.70  
  Purchase #2 $219.74   11.339%   $244.6563   $244.66   $244.65   $244.70  
  Purchase #3 $217.83   11.263%   $242.3642   $242.36   $242.35   $242.40  
  Purchase #4 $203.50   9.618%   $223.0726   $223.07   $223.05   $223.10  
  Purchase #5 $218.85   9.303%   $239.2096   $239.21   $239.20   $239.20  
  Purchase #6 $185.46   8.762%   $201.71   $201.71   $201.70   $201.70  
  Purchase #7 $226.80   4.179%   $236.278   $236.28   $236.30   $236.30  
  7 purchase totals = $1,339.95       $1,460.0377   $1,460.04   $1,460.00   $1,460.10