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 $216.86   4.690%   $227.0307   $227.03   $227.05   $227.00  
  Purchase #2 $169.33   8.197%   $183.21   $183.21   $183.20   $183.20  
  Purchase #3 $68.55   9.345%   $74.956   $74.96   $74.95   $75.00  
  Purchase #4 $203.40   11.755%   $227.3097   $227.31   $227.30   $227.30  
  Purchase #5 $70.37   4.165%   $73.3009   $73.30   $73.30   $73.30  
  Purchase #6 $211.28   7.457%   $227.0351   $227.04   $227.05   $227.00  
  Purchase #7 $14.75   13.852%   $16.7932   $16.79   $16.80   $16.80  
  7 purchase totals = $954.54       $1,029.6356   $1,029.64   $1,029.65   $1,029.60