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   5.645%   $125.0414   $125.04   $125.05   $125.00  
  Purchase #2 $168.61   6.270%   $179.1818   $179.18   $179.20   $179.20  
  Purchase #3 $24.50   3.686%   $25.4031   $25.40   $25.40   $25.40  
  Purchase #4 $199.73   9.697%   $219.0978   $219.10   $219.10   $219.10  
  Purchase #5 $240.79   5.190%   $253.287   $253.29   $253.30   $253.30  
  Purchase #6 $46.42   10.481%   $51.2853   $51.29   $51.30   $51.30  
  Purchase #7 $149.27   7.549%   $160.5384   $160.54   $160.55   $160.50  
  7 purchase totals = $947.68       $1,013.8348   $1,013.84   $1,013.90   $1,013.80