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 $118.36   5.643%   $125.0391   $125.04   $125.05   $125.00  
  Purchase #2 $223.41   11.686%   $249.5177   $249.52   $249.50   $249.50  
  Purchase #3 $172.73   9.495%   $189.1307   $189.13   $189.15   $189.10  
  Purchase #4 $210.59   5.186%   $221.5112   $221.51   $221.50   $221.50  
  Purchase #5 $165.46   4.348%   $172.6542   $172.65   $172.65   $172.70  
  Purchase #6 $39.29   8.148%   $42.4913   $42.49   $42.50   $42.50  
  Purchase #7 $221.63   13.703%   $252   $252.00   $252.00   $252.00  
  7 purchase totals = $1,151.47       $1,252.3442   $1,252.34   $1,252.35   $1,252.30