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 $200.25   11.694%   $223.6672   $223.67   $223.65   $223.70  
  Purchase #2 $216.79   13.306%   $245.6361   $245.64   $245.65   $245.60  
  Purchase #3 $153.94   8.672%   $167.2897   $167.29   $167.30   $167.30  
  Purchase #4 $74.99   3.160%   $77.3597   $77.36   $77.35   $77.40  
  Purchase #5 $64.54   11.638%   $72.0512   $72.05   $72.05   $72.10  
  Purchase #6 $120.79   4.583%   $126.3258   $126.33   $126.35   $126.30  
  Purchase #7 $142.73   6.728%   $152.3329   $152.33   $152.35   $152.30  
  7 purchase totals = $974.03       $1,064.6626   $1,064.67   $1,064.70   $1,064.70