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	$151.46	13.872%	$172.4705	$172.47	$172.45	$172.50
Purchase #2	$37.99	11.465%	$42.3456	$42.35	$42.35	$42.30
Purchase #3	$220.85	6.679%	$235.6006	$235.60	$235.60	$235.60
Purchase #4	$94.61	4.521%	$98.8873	$98.89	$98.90	$98.90
Purchase #5	$165.32	5.285%	$174.0572	$174.06	$174.05	$174.10
Purchase #6	$170.47	7.685%	$183.5706	$183.57	$183.55	$183.60
Purchase #7	$111.81	4.616%	$116.9711	$116.97	$116.95	$117.00
7 purchase totals =	$952.51		$1,023.9029	$1,023.91	$1,023.85	$1,024.00