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	$155.79	12.274%	$174.9117	$174.91	$174.90	$174.90
Purchase #2	$57.26	6.600%	$61.0392	$61.04	$61.05	$61.00
Purchase #3	$218.93	10.155%	$241.1623	$241.16	$241.15	$241.20
Purchase #4	$154.86	11.151%	$172.1284	$172.13	$172.15	$172.10
Purchase #5	$51.45	13.595%	$58.4446	$58.44	$58.45	$58.40
Purchase #6	$190.97	10.440%	$210.9073	$210.91	$210.90	$210.90
Purchase #7	$96.60	7.852%	$104.185	$104.19	$104.20	$104.20
7 purchase totals =	$925.86		$1,022.7785	$1,022.78	$1,022.80	$1,022.70