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	$44.33	5.867%	$46.9308	$46.93	$46.95	$46.90
Purchase #2	$34.49	11.633%	$38.5022	$38.50	$38.50	$38.50
Purchase #3	$246.64	13.147%	$279.0658	$279.07	$279.05	$279.10
Purchase #4	$159.54	13.482%	$181.0492	$181.05	$181.05	$181.00
Purchase #5	$61.78	10.279%	$68.1304	$68.13	$68.15	$68.10
Purchase #6	$92.70	8.206%	$100.307	$100.31	$100.30	$100.30
Purchase #7	$101.74	9.436%	$111.3402	$111.34	$111.35	$111.30
7 purchase totals =	$741.22		$825.3256	$825.33	$825.35	$825.20