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 $63.82   8.149%   $69.0207   $69.02   $69.00   $69.00  
  Purchase #2 $213.93   7.645%   $230.2849   $230.28   $230.30   $230.30  
  Purchase #3 $241.81   7.838%   $260.7631   $260.76   $260.75   $260.80  
  Purchase #4 $132.28   3.297%   $136.6413   $136.64   $136.65   $136.60  
  Purchase #5 $218.35   4.194%   $227.5076   $227.51   $227.50   $227.50  
  Purchase #6 $89.43   6.491%   $95.2349   $95.23   $95.25   $95.20  
  Purchase #7 $216.29   7.667%   $232.873   $232.87   $232.85   $232.90  
  7 purchase totals = $1,175.91       $1,252.3255   $1,252.31   $1,252.30   $1,252.30