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	$146.56	12.761%	$165.2625	$165.26	$165.25	$165.30
Purchase #2	$165.56	4.369%	$172.7933	$172.79	$172.80	$172.80
Purchase #3	$155.62	4.115%	$162.0238	$162.02	$162.00	$162.00
Purchase #4	$18.76	8.326%	$20.322	$20.32	$20.30	$20.30
Purchase #5	$240.52	8.138%	$260.0935	$260.09	$260.10	$260.10
Purchase #6	$188.77	10.505%	$208.6003	$208.60	$208.60	$208.60
Purchase #7	$91.59	7.586%	$98.538	$98.54	$98.55	$98.50
7 purchase totals =	$1,007.38		$1,087.6334	$1,087.62	$1,087.60	$1,087.60