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	$117.29	10.252%	$129.3146	$129.31	$129.30	$129.30
Purchase #2	$38.69	13.557%	$43.9352	$43.94	$43.95	$43.90
Purchase #3	$132.75	12.398%	$149.2083	$149.21	$149.20	$149.20
Purchase #4	$79.69	12.225%	$89.4321	$89.43	$89.45	$89.40
Purchase #5	$207.83	11.224%	$231.1568	$231.16	$231.15	$231.20
Purchase #6	$219.39	6.449%	$233.5385	$233.54	$233.55	$233.50
Purchase #7	$139.69	5.200%	$146.9539	$146.95	$146.95	$147.00
7 purchase totals =	$935.33		$1,023.5394	$1,023.54	$1,023.55	$1,023.50