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	$239.63	4.431%	$250.248	$250.25	$250.25	$250.20
Purchase #2	$19.30	11.417%	$21.5035	$21.50	$21.50	$21.50
Purchase #3	$145.37	4.746%	$152.2693	$152.27	$152.25	$152.30
Purchase #4	$52.48	12.795%	$59.1948	$59.19	$59.20	$59.20
Purchase #5	$226.49	13.102%	$256.1647	$256.16	$256.15	$256.20
Purchase #6	$144.32	5.639%	$152.4582	$152.46	$152.45	$152.50
Purchase #7	$153.93	3.599%	$159.4699	$159.47	$159.45	$159.50
7 purchase totals =	$981.52		$1,051.3084	$1,051.30	$1,051.25	$1,051.40