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	$146.96	5.701%	$155.3382	$155.34	$155.35	$155.30
Purchase #2	$242.56	8.120%	$262.2559	$262.26	$262.25	$262.30
Purchase #3	$18.45	9.108%	$20.1304	$20.13	$20.15	$20.10
Purchase #4	$112.88	13.296%	$127.8885	$127.89	$127.90	$127.90
Purchase #5	$206.70	12.626%	$232.7979	$232.80	$232.80	$232.80
Purchase #6	$204.42	9.130%	$223.0835	$223.08	$223.10	$223.10
Purchase #7	$39.49	13.749%	$44.9195	$44.92	$44.90	$44.90
7 purchase totals =	$971.46		$1,066.4139	$1,066.42	$1,066.45	$1,066.40