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	$195.38	11.836%	$218.5052	$218.51	$218.50	$218.50
Purchase #2	$78.87	6.701%	$84.1551	$84.16	$84.15	$84.20
Purchase #3	$42.93	13.357%	$48.6642	$48.66	$48.65	$48.70
Purchase #4	$49.73	9.711%	$54.5593	$54.56	$54.55	$54.60
Purchase #5	$120.27	3.390%	$124.3472	$124.35	$124.35	$124.30
Purchase #6	$33.80	5.780%	$35.7536	$35.75	$35.75	$35.80
Purchase #7	$146.40	4.121%	$152.4331	$152.43	$152.45	$152.40
7 purchase totals =	$667.38		$718.4177	$718.42	$718.40	$718.50