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	$245.46	8.480%	$266.275	$266.28	$266.30	$266.30
Purchase #2	$100.95	4.336%	$105.3272	$105.33	$105.35	$105.30
Purchase #3	$244.68	6.305%	$260.1071	$260.11	$260.10	$260.10
Purchase #4	$211.36	10.656%	$233.8825	$233.88	$233.90	$233.90
Purchase #5	$63.49	11.240%	$70.6263	$70.63	$70.65	$70.60
Purchase #6	$66.27	8.296%	$71.7678	$71.77	$71.75	$71.80
Purchase #7	$173.31	4.109%	$180.4313	$180.43	$180.45	$180.40
7 purchase totals =	$1,105.52		$1,188.4172	$1,188.43	$1,188.50	$1,188.40