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	$225.45	13.758%	$256.4674	$256.47	$256.45	$256.50
Purchase #2	$98.27	13.380%	$111.4185	$111.42	$111.40	$111.40
Purchase #3	$223.78	5.301%	$235.6426	$235.64	$235.65	$235.60
Purchase #4	$232.59	6.279%	$247.1943	$247.19	$247.20	$247.20
Purchase #5	$77.42	11.673%	$86.4572	$86.46	$86.45	$86.50
Purchase #6	$177.86	12.805%	$200.635	$200.64	$200.65	$200.60
Purchase #7	$53.52	10.767%	$59.2825	$59.28	$59.30	$59.30
7 purchase totals =	$1,088.89		$1,197.0975	$1,197.10	$1,197.10	$1,197.10