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	$185.28	5.699%	$195.8391	$195.84	$195.85	$195.80
Purchase #2	$224.30	10.835%	$248.6029	$248.60	$248.60	$248.60
Purchase #3	$61.54	5.449%	$64.8933	$64.89	$64.90	$64.90
Purchase #4	$173.78	10.156%	$191.4291	$191.43	$191.45	$191.40
Purchase #5	$127.77	12.692%	$143.9866	$143.99	$144.00	$144.00
Purchase #6	$136.86	3.673%	$141.8869	$141.89	$141.90	$141.90
Purchase #7	$238.56	6.250%	$253.47	$253.47	$253.45	$253.50
7 purchase totals =	$1,148.09		$1,240.1079	$1,240.11	$1,240.15	$1,240.10