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	$213.70	8.217%	$231.2597	$231.26	$231.25	$231.30
Purchase #2	$242.30	3.211%	$250.0803	$250.08	$250.10	$250.10
Purchase #3	$121.94	4.632%	$127.5883	$127.59	$127.60	$127.60
Purchase #4	$5.29	10.173%	$5.8282	$5.83	$5.85	$5.80
Purchase #5	$98.67	6.512%	$105.0954	$105.10	$105.10	$105.10
Purchase #6	$145.99	9.388%	$159.6955	$159.70	$159.70	$159.70
Purchase #7	$204.44	12.314%	$229.6147	$229.61	$229.60	$229.60
7 purchase totals =	$1,032.33		$1,109.1621	$1,109.17	$1,109.20	$1,109.20