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	$238.87	9.187%	$260.815	$260.82	$260.80	$260.80
Purchase #2	$58.93	12.716%	$66.4235	$66.42	$66.40	$66.40
Purchase #3	$45.58	10.514%	$50.3723	$50.37	$50.35	$50.40
Purchase #4	$248.83	6.111%	$264.036	$264.04	$264.05	$264.00
Purchase #5	$144.89	10.352%	$159.889	$159.89	$159.90	$159.90
Purchase #6	$188.65	7.361%	$202.5365	$202.54	$202.55	$202.50
Purchase #7	$14.73	4.174%	$15.3448	$15.34	$15.35	$15.30
7 purchase totals =	$940.48		$1,019.4171	$1,019.42	$1,019.40	$1,019.30