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 $68.57   12.384%   $77.0617   $77.06   $77.05   $77.10  
  Purchase #2 $244.55   6.554%   $260.5778   $260.58   $260.60   $260.60  
  Purchase #3 $137.63   5.449%   $145.1295   $145.13   $145.15   $145.10  
  Purchase #4 $119.56   5.776%   $126.4658   $126.47   $126.45   $126.50  
  Purchase #5 $246.31   6.848%   $263.1773   $263.18   $263.20   $263.20  
  Purchase #6 $243.96   9.870%   $268.0389   $268.04   $268.05   $268.00  
  Purchase #7 $101.73   10.300%   $112.2082   $112.21   $112.20   $112.20  
  7 purchase totals = $1,162.31       $1,252.6592   $1,252.67   $1,252.70   $1,252.70