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 $95.28   8.868%   $103.7294   $103.73   $103.75   $103.70  
  Purchase #2 $174.27   4.488%   $182.0912   $182.09   $182.10   $182.10  
  Purchase #3 $228.40   7.250%   $244.959   $244.96   $244.95   $245.00  
  Purchase #4 $82.63   13.514%   $93.7966   $93.80   $93.80   $93.80  
  Purchase #5 $70.78   6.238%   $75.1953   $75.20   $75.20   $75.20  
  Purchase #6 $151.79   8.414%   $164.5616   $164.56   $164.55   $164.60  
  Purchase #7 $147.84   10.497%   $163.3588   $163.36   $163.35   $163.40  
  7 purchase totals = $950.99       $1,027.6919   $1,027.70   $1,027.70   $1,027.80