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 $69.36   4.203%   $72.2752   $72.28   $72.30   $72.30  
  Purchase #2 $215.81   9.482%   $236.2731   $236.27   $236.25   $236.30  
  Purchase #3 $39.96   12.514%   $44.9606   $44.96   $44.95   $45.00  
  Purchase #4 $249.95   6.834%   $267.0316   $267.03   $267.05   $267.00  
  Purchase #5 $124.39   5.179%   $130.8322   $130.83   $130.85   $130.80  
  Purchase #6 $36.94   5.662%   $39.0315   $39.03   $39.05   $39.00  
  Purchase #7 $64.84   8.813%   $70.5543   $70.55   $70.55   $70.60  
  7 purchase totals = $801.25       $860.9585   $860.95   $861.00   $861.00