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 $119.69   4.442%   $125.0066   $125.01   $125.00   $125.00  
  Purchase #2 $33.71   3.380%   $34.8494   $34.85   $34.85   $34.80  
  Purchase #3 $244.44   8.851%   $266.0754   $266.08   $266.10   $266.10  
  Purchase #4 $237.27   3.425%   $245.3965   $245.40   $245.40   $245.40  
  Purchase #5 $194.76   4.521%   $203.5651   $203.57   $203.55   $203.60  
  Purchase #6 $238.25   9.385%   $260.6098   $260.61   $260.60   $260.60  
  Purchase #7 $192.89   6.597%   $205.615   $205.62   $205.60   $205.60  
  7 purchase totals = $1,261.01       $1,341.1178   $1,341.14   $1,341.10   $1,341.10