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	$44.26	10.339%	$48.836	$48.84	$48.85	$48.80
Purchase #2	$59.61	5.108%	$62.6549	$62.65	$62.65	$62.70
Purchase #3	$110.74	11.560%	$123.5415	$123.54	$123.55	$123.50
Purchase #4	$127.94	13.579%	$145.313	$145.31	$145.30	$145.30
Purchase #5	$205.46	11.225%	$228.5229	$228.52	$228.50	$228.50
Purchase #6	$45.73	4.486%	$47.7814	$47.78	$47.80	$47.80
Purchase #7	$154.76	9.772%	$169.8831	$169.88	$169.90	$169.90
7 purchase totals =	$748.50		$826.5328	$826.52	$826.55	$826.50