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	$177.46	9.259%	$193.891	$193.89	$193.90	$193.90
Purchase #2	$48.89	5.465%	$51.5618	$51.56	$51.55	$51.60
Purchase #3	$47.39	6.677%	$50.5542	$50.55	$50.55	$50.60
Purchase #4	$52.77	3.243%	$54.4813	$54.48	$54.50	$54.50
Purchase #5	$100.73	13.310%	$114.1372	$114.14	$114.15	$114.10
Purchase #6	$200.78	4.304%	$209.4216	$209.42	$209.40	$209.40
Purchase #7	$141.38	12.140%	$158.5435	$158.54	$158.55	$158.50
7 purchase totals =	$769.40		$832.5906	$832.58	$832.60	$832.60