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	$71.59	4.209%	$74.6032	$74.60	$74.60	$74.60
Purchase #2	$50.26	10.485%	$55.5298	$55.53	$55.55	$55.50
Purchase #3	$223.34	8.443%	$242.1966	$242.20	$242.20	$242.20
Purchase #4	$9.34	11.468%	$10.4111	$10.41	$10.40	$10.40
Purchase #5	$69.69	4.592%	$72.8902	$72.89	$72.90	$72.90
Purchase #6	$35.63	10.417%	$39.3416	$39.34	$39.35	$39.30
Purchase #7	$86.92	13.539%	$98.6881	$98.69	$98.70	$98.70
7 purchase totals =	$546.77		$593.6606	$593.66	$593.70	$593.60