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	$156.47	12.307%	$175.7268	$175.73	$175.75	$175.70
Purchase #2	$238.35	6.357%	$253.5019	$253.50	$253.50	$253.50
Purchase #3	$157.32	5.499%	$165.971	$165.97	$165.95	$166.00
Purchase #4	$126.93	3.599%	$131.4982	$131.50	$131.50	$131.50
Purchase #5	$99.30	9.276%	$108.5111	$108.51	$108.50	$108.50
Purchase #6	$127.48	11.162%	$141.7093	$141.71	$141.70	$141.70
Purchase #7	$157.33	9.604%	$172.44	$172.44	$172.45	$172.40
7 purchase totals =	$1,063.18		$1,149.3583	$1,149.36	$1,149.35	$1,149.30