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	$209.26	10.168%	$230.5376	$230.54	$230.55	$230.50
Purchase #2	$132.59	13.803%	$150.8914	$150.89	$150.90	$150.90
Purchase #3	$67.97	6.562%	$72.4302	$72.43	$72.45	$72.40
Purchase #4	$175.86	13.568%	$199.7207	$199.72	$199.70	$199.70
Purchase #5	$151.42	10.705%	$167.6295	$167.63	$167.65	$167.60
Purchase #6	$196.70	10.367%	$217.0919	$217.09	$217.10	$217.10
Purchase #7	$50.43	6.855%	$53.887	$53.89	$53.90	$53.90
7 purchase totals =	$984.23		$1,092.1883	$1,092.19	$1,092.25	$1,092.10