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	$118.76	6.213%	$126.1386	$126.14	$126.15	$126.10
Purchase #2	$35.58	4.502%	$37.1818	$37.18	$37.20	$37.20
Purchase #3	$93.75	13.849%	$106.7334	$106.73	$106.75	$106.70
Purchase #4	$61.30	13.720%	$69.7104	$69.71	$69.70	$69.70
Purchase #5	$10.72	4.766%	$11.2309	$11.23	$11.25	$11.20
Purchase #6	$81.37	11.395%	$90.6421	$90.64	$90.65	$90.60
Purchase #7	$28.76	12.627%	$32.3915	$32.39	$32.40	$32.40
7 purchase totals =	$430.24		$474.0287	$474.02	$474.10	$473.90