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	$186.69	11.454%	$208.0735	$208.07	$208.05	$208.10
Purchase #2	$44.73	13.522%	$50.7784	$50.78	$50.80	$50.80
Purchase #3	$122.78	3.591%	$127.189	$127.19	$127.20	$127.20
Purchase #4	$196.74	10.501%	$217.3997	$217.40	$217.40	$217.40
Purchase #5	$143.95	10.301%	$158.7783	$158.78	$158.80	$158.80
Purchase #6	$118.30	7.646%	$127.3452	$127.35	$127.35	$127.30
Purchase #7	$36.61	5.267%	$38.5382	$38.54	$38.55	$38.50
7 purchase totals =	$849.80		$928.1023	$928.11	$928.15	$928.10