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	$40.39	9.736%	$44.3224	$44.32	$44.30	$44.30
Purchase #2	$41.40	13.823%	$47.1227	$47.12	$47.10	$47.10
Purchase #3	$167.33	7.295%	$179.5367	$179.54	$179.55	$179.50
Purchase #4	$43.63	4.316%	$45.5131	$45.51	$45.50	$45.50
Purchase #5	$9.95	6.105%	$10.5574	$10.56	$10.55	$10.60
Purchase #6	$111.80	7.435%	$120.1123	$120.11	$120.10	$120.10
Purchase #7	$29.52	8.385%	$31.9953	$32.00	$32.00	$32.00
7 purchase totals =	$444.02		$479.1599	$479.16	$479.10	$479.10