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	$167.91	10.638%	$185.7723	$185.77	$185.75	$185.80
Purchase #2	$121.87	4.495%	$127.3481	$127.35	$127.35	$127.30
Purchase #3	$178.68	6.682%	$190.6194	$190.62	$190.60	$190.60
Purchase #4	$121.51	12.704%	$136.9466	$136.95	$136.95	$136.90
Purchase #5	$219.91	9.864%	$241.6019	$241.60	$241.60	$241.60
Purchase #6	$56.41	12.131%	$63.2531	$63.25	$63.25	$63.30
Purchase #7	$98.97	12.384%	$111.2264	$111.23	$111.25	$111.20
7 purchase totals =	$965.26		$1,056.7678	$1,056.77	$1,056.75	$1,056.70