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	$208.59	10.129%	$229.7181	$229.72	$229.70	$229.70
Purchase #2	$50.39	8.717%	$54.7825	$54.78	$54.80	$54.80
Purchase #3	$12.51	8.573%	$13.5825	$13.58	$13.60	$13.60
Purchase #4	$49.71	9.162%	$54.2644	$54.26	$54.25	$54.30
Purchase #5	$231.28	4.808%	$242.3999	$242.40	$242.40	$242.40
Purchase #6	$174.78	6.157%	$185.5412	$185.54	$185.55	$185.50
Purchase #7	$129.76	5.400%	$136.767	$136.77	$136.75	$136.80
7 purchase totals =	$857.02		$917.0556	$917.05	$917.05	$917.10