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	$171.54	5.790%	$181.4722	$181.47	$181.45	$181.50
Purchase #2	$60.39	9.376%	$66.0522	$66.05	$66.05	$66.10
Purchase #3	$9.46	12.167%	$10.611	$10.61	$10.60	$10.60
Purchase #4	$57.42	9.873%	$63.0891	$63.09	$63.10	$63.10
Purchase #5	$16.63	9.470%	$18.2049	$18.20	$18.20	$18.20
Purchase #6	$64.42	12.600%	$72.5369	$72.54	$72.55	$72.50
Purchase #7	$28.92	13.355%	$32.7823	$32.78	$32.80	$32.80
7 purchase totals =	$408.78		$444.7486	$444.74	$444.75	$444.80