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	$190.34	9.191%	$207.8341	$207.83	$207.85	$207.80
Purchase #2	$49.65	13.706%	$56.455	$56.46	$56.45	$56.50
Purchase #3	$243.49	6.238%	$258.6789	$258.68	$258.70	$258.70
Purchase #4	$90.82	9.334%	$99.2971	$99.30	$99.30	$99.30
Purchase #5	$156.92	5.218%	$165.1081	$165.11	$165.10	$165.10
Purchase #6	$97.92	10.579%	$108.279	$108.28	$108.30	$108.30
Purchase #7	$68.27	6.702%	$72.8455	$72.85	$72.85	$72.80
7 purchase totals =	$897.41		$968.4977	$968.51	$968.55	$968.50