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	$106.68	4.282%	$111.248	$111.25	$111.25	$111.20
Purchase #2	$217.38	10.165%	$239.4767	$239.48	$239.50	$239.50
Purchase #3	$113.30	13.515%	$128.6125	$128.61	$128.60	$128.60
Purchase #4	$141.73	8.521%	$153.8068	$153.81	$153.80	$153.80
Purchase #5	$110.45	5.305%	$116.3094	$116.31	$116.30	$116.30
Purchase #6	$96.82	13.803%	$110.1841	$110.18	$110.20	$110.20
Purchase #7	$155.72	3.252%	$160.784	$160.78	$160.80	$160.80
7 purchase totals =	$942.08		$1,020.4215	$1,020.42	$1,020.45	$1,020.40