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	$133.28	11.452%	$148.5432	$148.54	$148.55	$148.50
Purchase #2	$36.31	9.823%	$39.8767	$39.88	$39.90	$39.90
Purchase #3	$81.82	5.304%	$86.1597	$86.16	$86.15	$86.20
Purchase #4	$177.94	3.102%	$183.4597	$183.46	$183.45	$183.50
Purchase #5	$100.47	11.208%	$111.7307	$111.73	$111.75	$111.70
Purchase #6	$59.53	10.379%	$65.7086	$65.71	$65.70	$65.70
Purchase #7	$146.83	13.251%	$166.2864	$166.29	$166.30	$166.30
7 purchase totals =	$736.18		$801.7650	$801.77	$801.80	$801.80