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 $87.28   10.713%   $96.6303   $96.63   $96.65   $96.60  
  Purchase #2 $215.69   9.417%   $236.0015   $236.00   $236.00   $236.00  
  Purchase #3 $189.29   10.838%   $209.8053   $209.81   $209.80   $209.80  
  Purchase #4 $154.87   13.305%   $175.4755   $175.48   $175.50   $175.50  
  Purchase #5 $132.64   13.339%   $150.3328   $150.33   $150.35   $150.30  
  Purchase #6 $85.64   6.596%   $91.2888   $91.29   $91.30   $91.30  
  Purchase #7 $68.55   7.683%   $73.8167   $73.82   $73.80   $73.80  
  7 purchase totals = $933.96       $1,033.3509   $1,033.36   $1,033.40   $1,033.30