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	$165.30	9.635%	$181.2267	$181.23	$181.25	$181.20
Purchase #2	$60.50	6.795%	$64.611	$64.61	$64.60	$64.60
Purchase #3	$53.95	13.205%	$61.0741	$61.07	$61.05	$61.10
Purchase #4	$73.57	5.601%	$77.6907	$77.69	$77.70	$77.70
Purchase #5	$63.28	12.643%	$71.2805	$71.28	$71.30	$71.30
Purchase #6	$73.25	11.228%	$81.4745	$81.47	$81.45	$81.50
Purchase #7	$229.45	8.310%	$248.5173	$248.52	$248.50	$248.50
7 purchase totals =	$719.30		$785.8748	$785.87	$785.85	$785.90