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	$117.66	8.499%	$127.6599	$127.66	$127.65	$127.70
Purchase #2	$186.69	5.403%	$196.7769	$196.78	$196.80	$196.80
Purchase #3	$9.45	13.728%	$10.7473	$10.75	$10.75	$10.70
Purchase #4	$112.30	7.513%	$120.7371	$120.74	$120.75	$120.70
Purchase #5	$48.76	5.847%	$51.611	$51.61	$51.60	$51.60
Purchase #6	$194.83	13.608%	$221.3425	$221.34	$221.35	$221.30
Purchase #7	$137.51	12.516%	$154.7208	$154.72	$154.70	$154.70
7 purchase totals =	$807.20		$883.5955	$883.60	$883.60	$883.50