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 $60.54   11.468%   $67.4827   $67.48   $67.50   $67.50  
  Purchase #2 $216.57   8.107%   $234.1273   $234.13   $234.15   $234.10  
  Purchase #3 $95.41   8.786%   $103.7927   $103.79   $103.80   $103.80  
  Purchase #4 $178.56   7.444%   $191.852   $191.85   $191.85   $191.90  
  Purchase #5 $80.36   5.717%   $84.9542   $84.95   $84.95   $85.00  
  Purchase #6 $250.86   8.486%   $272.148   $272.15   $272.15   $272.10  
  Purchase #7 $236.64   5.570%   $249.8208   $249.82   $249.80   $249.80  
  7 purchase totals = $1,118.94       $1,204.1777   $1,204.17   $1,204.20   $1,204.20