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	$64.34	13.215%	$72.8425	$72.84	$72.85	$72.80
Purchase #2	$127.58	12.356%	$143.3438	$143.34	$143.35	$143.30
Purchase #3	$217.59	4.830%	$228.0996	$228.10	$228.10	$228.10
Purchase #4	$117.88	12.393%	$132.4889	$132.49	$132.50	$132.50
Purchase #5	$56.69	13.162%	$64.1515	$64.15	$64.15	$64.20
Purchase #6	$241.47	7.796%	$260.295	$260.30	$260.30	$260.30
Purchase #7	$100.42	6.825%	$107.2737	$107.27	$107.25	$107.30
7 purchase totals =	$925.97		$1,008.4950	$1,008.49	$1,008.50	$1,008.50