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	$34.74	11.388%	$38.6962	$38.70	$38.70	$38.70
Purchase #2	$47.43	12.790%	$53.4963	$53.50	$53.50	$53.50
Purchase #3	$90.89	4.784%	$95.2382	$95.24	$95.25	$95.20
Purchase #4	$7.42	11.844%	$8.2988	$8.30	$8.30	$8.30
Purchase #5	$218.84	5.610%	$231.1169	$231.12	$231.10	$231.10
Purchase #6	$113.60	12.318%	$127.5932	$127.59	$127.60	$127.60
Purchase #7	$6.85	8.173%	$7.4099	$7.41	$7.40	$7.40
7 purchase totals =	$519.77		$561.8495	$561.86	$561.85	$561.80