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	$130.97	9.521%	$143.4397	$143.44	$143.45	$143.40
Purchase #2	$35.48	7.371%	$38.0952	$38.10	$38.10	$38.10
Purchase #3	$171.77	9.722%	$188.4695	$188.47	$188.45	$188.50
Purchase #4	$60.79	7.335%	$65.2489	$65.25	$65.25	$65.20
Purchase #5	$114.33	11.773%	$127.7901	$127.79	$127.80	$127.80
Purchase #6	$30.84	11.238%	$34.3058	$34.31	$34.30	$34.30
Purchase #7	$99.70	13.368%	$113.0279	$113.03	$113.05	$113.00
7 purchase totals =	$643.88		$710.3771	$710.39	$710.40	$710.30