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 $34.57   6.601%   $36.852   $36.85   $36.85   $36.90  
  Purchase #2 $65.70   11.581%   $73.3087   $73.31   $73.30   $73.30  
  Purchase #3 $180.28   3.119%   $185.9029   $185.90   $185.90   $185.90  
  Purchase #4 $188.86   5.300%   $198.8696   $198.87   $198.85   $198.90  
  Purchase #5 $93.65   4.608%   $97.9654   $97.97   $97.95   $98.00  
  Purchase #6 $143.56   4.821%   $150.481   $150.48   $150.50   $150.50  
  Purchase #7 $190.32   10.855%   $210.9792   $210.98   $211.00   $211.00  
  7 purchase totals = $896.94       $954.3588   $954.36   $954.35   $954.50