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	$137.57	12.496%	$154.7607	$154.76	$154.75	$154.80
Purchase #2	$235.60	11.236%	$262.072	$262.07	$262.05	$262.10
Purchase #3	$116.66	9.345%	$127.5619	$127.56	$127.55	$127.60
Purchase #4	$54.40	11.274%	$60.5331	$60.53	$60.55	$60.50
Purchase #5	$228.85	12.865%	$258.2916	$258.29	$258.30	$258.30
Purchase #6	$32.29	9.798%	$35.4538	$35.45	$35.45	$35.50
Purchase #7	$49.28	7.475%	$52.9637	$52.96	$52.95	$53.00
7 purchase totals =	$854.65		$951.6368	$951.62	$951.60	$951.80