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	$115.25	10.616%	$127.4849	$127.48	$127.50	$127.50
Purchase #2	$191.30	7.585%	$205.8101	$205.81	$205.80	$205.80
Purchase #3	$48.67	6.453%	$51.8107	$51.81	$51.80	$51.80
Purchase #4	$195.85	12.680%	$220.6838	$220.68	$220.70	$220.70
Purchase #5	$130.85	4.869%	$137.2211	$137.22	$137.20	$137.20
Purchase #6	$123.45	4.859%	$129.4484	$129.45	$129.45	$129.40
Purchase #7	$55.36	7.614%	$59.5751	$59.58	$59.60	$59.60
7 purchase totals =	$860.73		$932.0341	$932.03	$932.05	$932.00