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	$184.51	5.429%	$194.527	$194.53	$194.55	$194.50
Purchase #2	$174.50	8.546%	$189.4128	$189.41	$189.40	$189.40
Purchase #3	$53.54	13.802%	$60.9296	$60.93	$60.95	$60.90
Purchase #4	$42.35	7.168%	$45.3856	$45.39	$45.40	$45.40
Purchase #5	$9.68	6.191%	$10.2793	$10.28	$10.30	$10.30
Purchase #6	$61.83	5.823%	$65.4304	$65.43	$65.45	$65.40
Purchase #7	$28.56	9.642%	$31.3138	$31.31	$31.30	$31.30
7 purchase totals =	$554.97		$597.2785	$597.28	$597.35	$597.20