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	$149.66	6.361%	$159.1799	$159.18	$159.20	$159.20
Purchase #2	$232.87	6.574%	$248.1789	$248.18	$248.20	$248.20
Purchase #3	$68.86	6.274%	$73.1803	$73.18	$73.20	$73.20
Purchase #4	$213.90	12.851%	$241.3883	$241.39	$241.40	$241.40
Purchase #5	$157.91	9.497%	$172.9067	$172.91	$172.90	$172.90
Purchase #6	$37.67	7.257%	$40.4037	$40.40	$40.40	$40.40
Purchase #7	$138.96	8.865%	$151.2788	$151.28	$151.30	$151.30
7 purchase totals =	$999.83		$1,086.5166	$1,086.52	$1,086.60	$1,086.60