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	$120.89	10.738%	$133.8712	$133.87	$133.85	$133.90
Purchase #2	$50.37	5.501%	$53.1409	$53.14	$53.15	$53.10
Purchase #3	$11.30	13.429%	$12.8175	$12.82	$12.80	$12.80
Purchase #4	$84.30	9.826%	$92.5833	$92.58	$92.60	$92.60
Purchase #5	$72.78	10.850%	$80.6766	$80.68	$80.70	$80.70
Purchase #6	$130.78	11.567%	$145.9073	$145.91	$145.90	$145.90
Purchase #7	$226.74	12.242%	$254.4975	$254.50	$254.50	$254.50
7 purchase totals =	$697.16		$773.4943	$773.50	$773.50	$773.50