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	$180.61	5.357%	$190.2853	$190.29	$190.30	$190.30
Purchase #2	$153.74	3.709%	$159.4422	$159.44	$159.45	$159.40
Purchase #3	$199.84	10.789%	$221.4007	$221.40	$221.40	$221.40
Purchase #4	$104.40	11.269%	$116.1648	$116.16	$116.15	$116.20
Purchase #5	$195.58	13.388%	$221.7643	$221.76	$221.75	$221.80
Purchase #6	$201.98	13.802%	$229.8573	$229.86	$229.85	$229.90
Purchase #7	$149.66	8.654%	$162.6116	$162.61	$162.60	$162.60
7 purchase totals =	$1,185.81		$1,301.5262	$1,301.52	$1,301.50	$1,301.60