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 $33.69   10.694%   $37.2928   $37.29   $37.30   $37.30  
  Purchase #2 $158.93   11.397%   $177.0433   $177.04   $177.05   $177.00  
  Purchase #3 $245.58   3.218%   $253.4828   $253.48   $253.50   $253.50  
  Purchase #4 $150.75   13.152%   $170.5766   $170.58   $170.60   $170.60  
  Purchase #5 $98.97   6.385%   $105.2892   $105.29   $105.30   $105.30  
  Purchase #6 $201.46   8.603%   $218.7916   $218.79   $218.80   $218.80  
  Purchase #7 $139.73   8.802%   $152.029   $152.03   $152.05   $152.00  
  7 purchase totals = $1,029.11       $1,114.5053   $1,114.50   $1,114.60   $1,114.50