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	$163.30	9.367%	$178.5963	$178.60	$178.60	$178.60
Purchase #2	$238.84	13.112%	$270.1567	$270.16	$270.15	$270.20
Purchase #3	$95.95	8.363%	$103.9743	$103.97	$103.95	$104.00
Purchase #4	$160.40	7.555%	$172.5182	$172.52	$172.50	$172.50
Purchase #5	$177.89	10.523%	$196.6094	$196.61	$196.60	$196.60
Purchase #6	$12.44	10.520%	$13.7487	$13.75	$13.75	$13.70
Purchase #7	$216.57	13.319%	$245.415	$245.42	$245.40	$245.40
7 purchase totals =	$1,065.39		$1,181.0186	$1,181.03	$1,180.95	$1,181.00