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	$33.46	11.665%	$37.3631	$37.36	$37.35	$37.40
Purchase #2	$90.33	11.499%	$100.717	$100.72	$100.70	$100.70
Purchase #3	$239.75	13.106%	$271.1716	$271.17	$271.15	$271.20
Purchase #4	$247.26	3.298%	$255.4146	$255.41	$255.40	$255.40
Purchase #5	$87.56	8.241%	$94.7758	$94.78	$94.80	$94.80
Purchase #6	$30.70	8.772%	$33.393	$33.39	$33.40	$33.40
Purchase #7	$62.87	10.167%	$69.262	$69.26	$69.25	$69.30
7 purchase totals =	$791.93		$862.0971	$862.09	$862.05	$862.20