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	$120.84	5.230%	$127.1599	$127.16	$127.15	$127.20
Purchase #2	$245.34	4.125%	$255.4603	$255.46	$255.45	$255.50
Purchase #3	$242.33	12.487%	$272.5897	$272.59	$272.60	$272.60
Purchase #4	$82.91	11.814%	$92.705	$92.71	$92.70	$92.70
Purchase #5	$216.92	12.735%	$244.5448	$244.54	$244.55	$244.50
Purchase #6	$229.39	8.784%	$249.5396	$249.54	$249.55	$249.50
Purchase #7	$182.35	10.265%	$201.0682	$201.07	$201.05	$201.10
7 purchase totals =	$1,320.08		$1,443.0675	$1,443.07	$1,443.05	$1,443.10