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	$182.51	11.313%	$203.1574	$203.16	$203.15	$203.20
Purchase #2	$55.45	10.804%	$61.4408	$61.44	$61.45	$61.40
Purchase #3	$229.25	9.273%	$250.5084	$250.51	$250.50	$250.50
Purchase #4	$148.58	11.462%	$165.6102	$165.61	$165.60	$165.60
Purchase #5	$240.60	6.110%	$255.3007	$255.30	$255.30	$255.30
Purchase #6	$68.56	3.677%	$71.081	$71.08	$71.10	$71.10
Purchase #7	$225.31	5.874%	$238.5447	$238.54	$238.55	$238.50
7 purchase totals =	$1,150.26		$1,245.6432	$1,245.64	$1,245.65	$1,245.60