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	$204.52	9.445%	$223.8369	$223.84	$223.85	$223.80
Purchase #2	$68.76	6.151%	$72.9894	$72.99	$73.00	$73.00
Purchase #3	$74.60	10.612%	$82.5166	$82.52	$82.50	$82.50
Purchase #4	$193.26	3.699%	$200.4087	$200.41	$200.40	$200.40
Purchase #5	$198.93	9.292%	$217.4146	$217.41	$217.40	$217.40
Purchase #6	$237.58	11.301%	$264.4289	$264.43	$264.45	$264.40
Purchase #7	$52.76	11.684%	$58.9245	$58.92	$58.90	$58.90
7 purchase totals =	$1,030.41		$1,120.5196	$1,120.52	$1,120.50	$1,120.40