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	$118.69	8.175%	$128.3929	$128.39	$128.40	$128.40
Purchase #2	$250.50	5.515%	$264.3151	$264.32	$264.30	$264.30
Purchase #3	$60.74	8.196%	$65.7183	$65.72	$65.70	$65.70
Purchase #4	$137.82	10.123%	$151.7715	$151.77	$151.75	$151.80
Purchase #5	$185.25	10.408%	$204.5308	$204.53	$204.55	$204.50
Purchase #6	$159.31	7.577%	$171.3809	$171.38	$171.40	$171.40
Purchase #7	$44.46	3.606%	$46.0632	$46.06	$46.05	$46.10
7 purchase totals =	$956.77		$1,032.1727	$1,032.17	$1,032.15	$1,032.20