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 $235.53   9.620%   $258.188   $258.19   $258.20   $258.20  
  Purchase #2 $125.48   5.157%   $131.951   $131.95   $131.95   $132.00  
  Purchase #3 $73.98   10.598%   $81.8204   $81.82   $81.80   $81.80  
  Purchase #4 $127.86   7.376%   $137.291   $137.29   $137.30   $137.30  
  Purchase #5 $158.31   5.238%   $166.6023   $166.60   $166.60   $166.60  
  Purchase #6 $177.28   11.332%   $197.3694   $197.37   $197.35   $197.40  
  Purchase #7 $96.28   5.669%   $101.7381   $101.74   $101.75   $101.70  
  7 purchase totals = $994.72       $1,074.9602   $1,074.96   $1,074.95   $1,075.00