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	$141.64	8.220%	$153.2828	$153.28	$153.30	$153.30
Purchase #2	$146.31	3.429%	$151.327	$151.33	$151.35	$151.30
Purchase #3	$59.92	11.154%	$66.6035	$66.60	$66.60	$66.60
Purchase #4	$175.40	4.180%	$182.7317	$182.73	$182.75	$182.70
Purchase #5	$52.33	9.464%	$57.2825	$57.28	$57.30	$57.30
Purchase #6	$137.34	7.825%	$148.0869	$148.09	$148.10	$148.10
Purchase #7	$200.80	4.592%	$210.0207	$210.02	$210.00	$210.00
7 purchase totals =	$913.74		$969.3351	$969.33	$969.40	$969.30