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	$192.77	9.697%	$211.4629	$211.46	$211.45	$211.50
Purchase #2	$141.67	13.133%	$160.2755	$160.28	$160.30	$160.30
Purchase #3	$205.89	9.215%	$224.8628	$224.86	$224.85	$224.90
Purchase #4	$50.26	6.235%	$53.3937	$53.39	$53.40	$53.40
Purchase #5	$117.52	12.315%	$131.9926	$131.99	$132.00	$132.00
Purchase #6	$137.25	10.113%	$151.1301	$151.13	$151.15	$151.10
Purchase #7	$196.48	8.565%	$213.3085	$213.31	$213.30	$213.30
7 purchase totals =	$1,041.84		$1,146.4261	$1,146.42	$1,146.45	$1,146.50