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	$183.90	9.245%	$200.9016	$200.90	$200.90	$200.90
Purchase #2	$224.65	12.859%	$253.5377	$253.54	$253.55	$253.50
Purchase #3	$207.27	9.241%	$226.4238	$226.42	$226.40	$226.40
Purchase #4	$219.90	6.186%	$233.503	$233.50	$233.50	$233.50
Purchase #5	$42.81	6.831%	$45.7344	$45.73	$45.75	$45.70
Purchase #6	$157.52	5.475%	$166.1442	$166.14	$166.15	$166.10
Purchase #7	$16.34	11.739%	$18.2582	$18.26	$18.25	$18.30
7 purchase totals =	$1,052.39		$1,144.5029	$1,144.49	$1,144.50	$1,144.40