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	$22.44	9.782%	$24.6351	$24.64	$24.65	$24.60
Purchase #2	$83.89	6.739%	$89.5433	$89.54	$89.55	$89.50
Purchase #3	$167.66	10.232%	$184.815	$184.82	$184.80	$184.80
Purchase #4	$234.25	4.518%	$244.8334	$244.83	$244.85	$244.80
Purchase #5	$97.31	4.157%	$101.3552	$101.36	$101.35	$101.40
Purchase #6	$93.49	12.361%	$105.0463	$105.05	$105.05	$105.00
Purchase #7	$166.64	4.195%	$173.6305	$173.63	$173.65	$173.60
7 purchase totals =	$865.68		$923.8588	$923.87	$923.90	$923.70