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	$164.40	5.546%	$173.5176	$173.52	$173.50	$173.50
Purchase #2	$96.83	3.195%	$99.9237	$99.92	$99.90	$99.90
Purchase #3	$237.37	5.396%	$250.1785	$250.18	$250.20	$250.20
Purchase #4	$197.95	9.318%	$216.395	$216.40	$216.40	$216.40
Purchase #5	$199.97	13.771%	$227.5079	$227.51	$227.50	$227.50
Purchase #6	$68.74	13.741%	$78.1856	$78.19	$78.20	$78.20
Purchase #7	$52.28	12.429%	$58.7779	$58.78	$58.80	$58.80
7 purchase totals =	$1,017.54		$1,104.4862	$1,104.50	$1,104.50	$1,104.50