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	$141.41	7.241%	$151.6495	$151.65	$151.65	$151.60
Purchase #2	$56.46	7.151%	$60.4975	$60.50	$60.50	$60.50
Purchase #3	$191.25	4.791%	$200.4128	$200.41	$200.40	$200.40
Purchase #4	$35.65	3.358%	$36.8471	$36.85	$36.85	$36.80
Purchase #5	$23.84	13.733%	$27.1139	$27.11	$27.10	$27.10
Purchase #6	$92.45	13.494%	$104.9252	$104.93	$104.95	$104.90
Purchase #7	$114.43	11.307%	$127.3686	$127.37	$127.35	$127.40
7 purchase totals =	$655.49		$708.8146	$708.82	$708.80	$708.70