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	$104.94	11.229%	$116.7237	$116.72	$116.70	$116.70
Purchase #2	$50.48	11.219%	$56.1434	$56.14	$56.15	$56.10
Purchase #3	$202.86	4.704%	$212.4025	$212.40	$212.40	$212.40
Purchase #4	$99.38	10.839%	$110.1518	$110.15	$110.15	$110.20
Purchase #5	$77.94	3.433%	$80.6157	$80.62	$80.60	$80.60
Purchase #6	$229.53	13.344%	$260.1585	$260.16	$260.15	$260.20
Purchase #7	$218.46	3.316%	$225.7041	$225.70	$225.70	$225.70
7 purchase totals =	$983.59		$1,061.8997	$1,061.89	$1,061.85	$1,061.90