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	$65.27	12.305%	$73.3015	$73.30	$73.30	$73.30
Purchase #2	$51.26	11.105%	$56.9524	$56.95	$56.95	$57.00
Purchase #3	$91.87	13.132%	$103.9344	$103.93	$103.95	$103.90
Purchase #4	$50.68	9.369%	$55.4282	$55.43	$55.45	$55.40
Purchase #5	$154.89	8.114%	$167.4578	$167.46	$167.45	$167.50
Purchase #6	$163.33	13.139%	$184.7899	$184.79	$184.80	$184.80
Purchase #7	$127.79	7.421%	$137.2733	$137.27	$137.25	$137.30
7 purchase totals =	$705.09		$779.1375	$779.13	$779.15	$779.20