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	$228.82	11.760%	$255.7292	$255.73	$255.75	$255.70
Purchase #2	$143.52	7.274%	$153.9596	$153.96	$153.95	$154.00
Purchase #3	$45.26	11.226%	$50.3409	$50.34	$50.35	$50.30
Purchase #4	$38.92	4.631%	$40.7224	$40.72	$40.70	$40.70
Purchase #5	$223.75	5.525%	$236.1122	$236.11	$236.10	$236.10
Purchase #6	$90.98	9.393%	$99.5258	$99.53	$99.55	$99.50
Purchase #7	$155.58	10.183%	$171.4227	$171.42	$171.40	$171.40
7 purchase totals =	$926.83		$1,007.8128	$1,007.81	$1,007.80	$1,007.70