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	$154.88	11.297%	$172.3768	$172.38	$172.40	$172.40
Purchase #2	$185.59	8.269%	$200.9364	$200.94	$200.95	$200.90
Purchase #3	$209.94	4.103%	$218.5538	$218.55	$218.55	$218.60
Purchase #4	$221.85	6.273%	$235.7667	$235.77	$235.75	$235.80
Purchase #5	$160.38	3.259%	$165.6068	$165.61	$165.60	$165.60
Purchase #6	$147.58	8.151%	$159.6092	$159.61	$159.60	$159.60
Purchase #7	$191.96	13.772%	$218.3967	$218.40	$218.40	$218.40
7 purchase totals =	$1,272.18		$1,371.2464	$1,371.26	$1,371.25	$1,371.30