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	$114.66	11.317%	$127.6361	$127.64	$127.65	$127.60
Purchase #2	$64.76	7.772%	$69.7931	$69.79	$69.80	$69.80
Purchase #3	$178.52	6.819%	$190.6933	$190.69	$190.70	$190.70
Purchase #4	$10.89	3.420%	$11.2624	$11.26	$11.25	$11.30
Purchase #5	$41.70	5.236%	$43.8834	$43.88	$43.90	$43.90
Purchase #6	$32.82	3.292%	$33.9004	$33.90	$33.90	$33.90
Purchase #7	$25.90	10.750%	$28.6843	$28.68	$28.70	$28.70
7 purchase totals =	$469.25		$505.8530	$505.84	$505.90	$505.90