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	$213.64	3.623%	$221.3802	$221.38	$221.40	$221.40
Purchase #2	$127.42	7.734%	$137.2747	$137.27	$137.25	$137.30
Purchase #3	$112.92	8.444%	$122.455	$122.46	$122.45	$122.50
Purchase #4	$218.69	12.271%	$245.5254	$245.53	$245.55	$245.50
Purchase #5	$53.96	13.858%	$61.4378	$61.44	$61.45	$61.40
Purchase #6	$172.90	13.569%	$196.3608	$196.36	$196.35	$196.40
Purchase #7	$212.43	11.150%	$236.1159	$236.12	$236.10	$236.10
7 purchase totals =	$1,111.96		$1,220.5498	$1,220.56	$1,220.55	$1,220.60