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	$221.33	5.171%	$232.775	$232.78	$232.80	$232.80
Purchase #2	$225.41	11.336%	$250.9625	$250.96	$250.95	$251.00
Purchase #3	$212.57	10.751%	$235.4234	$235.42	$235.40	$235.40
Purchase #4	$241.40	11.233%	$268.5165	$268.52	$268.50	$268.50
Purchase #5	$28.47	3.698%	$29.5228	$29.52	$29.50	$29.50
Purchase #6	$123.39	3.518%	$127.7309	$127.73	$127.75	$127.70
Purchase #7	$9.82	6.701%	$10.478	$10.48	$10.50	$10.50
7 purchase totals =	$1,062.39		$1,155.4091	$1,155.41	$1,155.40	$1,155.40