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 $220.96   11.806%   $247.0465   $247.05   $247.05   $247.00  
  Purchase #2 $151.60   10.753%   $167.9015   $167.90   $167.90   $167.90  
  Purchase #3 $53.99   6.416%   $57.454   $57.45   $57.45   $57.50  
  Purchase #4 $181.61   8.238%   $196.571   $196.57   $196.55   $196.60  
  Purchase #5 $161.85   11.598%   $180.6214   $180.62   $180.60   $180.60  
  Purchase #6 $20.55   3.283%   $21.2247   $21.22   $21.20   $21.20  
  Purchase #7 $233.38   4.482%   $243.8401   $243.84   $243.85   $243.80  
  7 purchase totals = $1,023.94       $1,114.6592   $1,114.65   $1,114.60   $1,114.60