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	$102.74	8.439%	$111.4102	$111.41	$111.40	$111.40
Purchase #2	$213.96	13.701%	$243.2747	$243.27	$243.25	$243.30
Purchase #3	$165.57	4.514%	$173.0438	$173.04	$173.05	$173.00
Purchase #4	$20.46	5.393%	$21.5634	$21.56	$21.55	$21.60
Purchase #5	$178.34	6.530%	$189.9856	$189.99	$190.00	$190.00
Purchase #6	$123.84	6.247%	$131.5763	$131.58	$131.60	$131.60
Purchase #7	$210.93	5.602%	$222.7463	$222.75	$222.75	$222.70
7 purchase totals =	$1,015.84		$1,093.6003	$1,093.60	$1,093.60	$1,093.60