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 $58.68   4.735%   $61.4585   $61.46   $61.45   $61.50  
  Purchase #2 $192.43   9.477%   $210.6666   $210.67   $210.65   $210.70  
  Purchase #3 $193.44   5.343%   $203.7755   $203.78   $203.80   $203.80  
  Purchase #4 $96.55   3.775%   $100.1948   $100.19   $100.20   $100.20  
  Purchase #5 $206.42   9.345%   $225.7099   $225.71   $225.70   $225.70  
  Purchase #6 $6.50   5.230%   $6.84   $6.84   $6.85   $6.80  
  Purchase #7 $202.88   6.360%   $215.7832   $215.78   $215.80   $215.80  
  7 purchase totals = $956.90       $1,024.4285   $1,024.43   $1,024.45   $1,024.50