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	$175.29	5.205%	$184.4138	$184.41	$184.40	$184.40
Purchase #2	$28.47	6.725%	$30.3846	$30.38	$30.40	$30.40
Purchase #3	$155.94	13.277%	$176.6442	$176.64	$176.65	$176.60
Purchase #4	$187.80	4.761%	$196.7412	$196.74	$196.75	$196.70
Purchase #5	$62.33	10.246%	$68.7163	$68.72	$68.70	$68.70
Purchase #6	$81.83	9.228%	$89.3813	$89.38	$89.40	$89.40
Purchase #7	$133.55	9.555%	$146.3107	$146.31	$146.30	$146.30
7 purchase totals =	$825.21		$892.5921	$892.58	$892.60	$892.50