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	$153.41	4.786%	$160.7522	$160.75	$160.75	$160.80
Purchase #2	$56.49	9.553%	$61.8865	$61.89	$61.90	$61.90
Purchase #3	$159.28	10.791%	$176.4679	$176.47	$176.45	$176.50
Purchase #4	$55.29	11.716%	$61.7678	$61.77	$61.75	$61.80
Purchase #5	$164.51	12.297%	$184.7398	$184.74	$184.75	$184.70
Purchase #6	$49.88	13.222%	$56.4751	$56.48	$56.50	$56.50
Purchase #7	$215.64	11.334%	$240.0806	$240.08	$240.10	$240.10
7 purchase totals =	$854.50		$942.1699	$942.18	$942.20	$942.30