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	$238.33	5.149%	$250.6016	$250.60	$250.60	$250.60
Purchase #2	$211.73	5.771%	$223.9489	$223.95	$223.95	$223.90
Purchase #3	$175.87	3.436%	$181.9129	$181.91	$181.90	$181.90
Purchase #4	$158.73	8.102%	$171.5903	$171.59	$171.60	$171.60
Purchase #5	$74.54	7.420%	$80.0709	$80.07	$80.05	$80.10
Purchase #6	$211.63	4.474%	$221.0983	$221.10	$221.10	$221.10
Purchase #7	$38.69	11.859%	$43.2782	$43.28	$43.30	$43.30
7 purchase totals =	$1,109.52		$1,172.5011	$1,172.50	$1,172.50	$1,172.50