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	$166.83	3.512%	$172.6891	$172.69	$172.70	$172.70
Purchase #2	$184.40	3.359%	$190.594	$190.59	$190.60	$190.60
Purchase #3	$57.47	8.551%	$62.3843	$62.38	$62.40	$62.40
Purchase #4	$109.83	3.445%	$113.6136	$113.61	$113.60	$113.60
Purchase #5	$64.54	10.450%	$71.2844	$71.28	$71.30	$71.30
Purchase #6	$52.32	13.474%	$59.3696	$59.37	$59.35	$59.40
Purchase #7	$99.65	5.153%	$104.785	$104.79	$104.80	$104.80
7 purchase totals =	$735.04		$774.7200	$774.71	$774.75	$774.80