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	$103.39	6.570%	$110.1827	$110.18	$110.20	$110.20
Purchase #2	$66.33	11.169%	$73.7384	$73.74	$73.75	$73.70
Purchase #3	$214.49	9.286%	$234.4075	$234.41	$234.40	$234.40
Purchase #4	$66.43	9.392%	$72.6691	$72.67	$72.65	$72.70
Purchase #5	$140.71	7.618%	$151.4293	$151.43	$151.45	$151.40
Purchase #6	$49.38	5.630%	$52.1601	$52.16	$52.15	$52.20
Purchase #7	$34.34	10.357%	$37.8966	$37.90	$37.90	$37.90
7 purchase totals =	$675.07		$732.4837	$732.49	$732.50	$732.50