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	$175.86	6.648%	$187.5512	$187.55	$187.55	$187.60
Purchase #2	$171.76	13.132%	$194.3155	$194.32	$194.30	$194.30
Purchase #3	$154.89	12.277%	$173.9058	$173.91	$173.90	$173.90
Purchase #4	$34.32	9.126%	$37.452	$37.45	$37.45	$37.50
Purchase #5	$60.94	7.798%	$65.6921	$65.69	$65.70	$65.70
Purchase #6	$40.88	13.798%	$46.5206	$46.52	$46.50	$46.50
Purchase #7	$93.61	3.431%	$96.8218	$96.82	$96.80	$96.80
7 purchase totals =	$732.26		$802.2590	$802.26	$802.20	$802.30