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	$80.54	13.592%	$91.487	$91.49	$91.50	$91.50
Purchase #2	$16.68	8.815%	$18.1503	$18.15	$18.15	$18.20
Purchase #3	$81.94	4.490%	$85.6191	$85.62	$85.60	$85.60
Purchase #4	$66.46	10.185%	$73.229	$73.23	$73.25	$73.20
Purchase #5	$99.53	11.860%	$111.3343	$111.33	$111.35	$111.30
Purchase #6	$233.69	9.704%	$256.3673	$256.37	$256.35	$256.40
Purchase #7	$100.75	10.567%	$111.3963	$111.40	$111.40	$111.40
7 purchase totals =	$679.59		$747.5833	$747.59	$747.60	$747.60