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	$233.76	11.342%	$260.2731	$260.27	$260.25	$260.30
Purchase #2	$235.35	10.279%	$259.5416	$259.54	$259.55	$259.50
Purchase #3	$211.68	11.849%	$236.762	$236.76	$236.75	$236.80
Purchase #4	$100.75	10.692%	$111.5222	$111.52	$111.50	$111.50
Purchase #5	$131.29	6.691%	$140.0746	$140.07	$140.05	$140.10
Purchase #6	$69.61	7.568%	$74.8781	$74.88	$74.90	$74.90
Purchase #7	$98.25	11.178%	$109.2324	$109.23	$109.25	$109.20
7 purchase totals =	$1,080.69		$1,192.2840	$1,192.27	$1,192.25	$1,192.30