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 $61.47   12.141%   $68.9331   $68.93   $68.95   $68.90  
  Purchase #2 $185.34   5.322%   $195.2038   $195.20   $195.20   $195.20  
  Purchase #3 $132.43   5.197%   $139.3124   $139.31   $139.30   $139.30  
  Purchase #4 $171.98   12.283%   $193.1043   $193.10   $193.10   $193.10  
  Purchase #5 $124.26   11.215%   $138.1958   $138.20   $138.20   $138.20  
  Purchase #6 $181.62   3.121%   $187.2884   $187.29   $187.30   $187.30  
  Purchase #7 $235.63   4.186%   $245.4935   $245.49   $245.50   $245.50  
  7 purchase totals = $1,092.73       $1,167.5313   $1,167.52   $1,167.55   $1,167.50