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	$156.50	10.449%	$172.8527	$172.85	$172.85	$172.90
Purchase #2	$228.33	11.856%	$255.4008	$255.40	$255.40	$255.40
Purchase #3	$165.48	8.729%	$179.9247	$179.92	$179.90	$179.90
Purchase #4	$158.85	6.425%	$169.0561	$169.06	$169.05	$169.10
Purchase #5	$38.39	9.803%	$42.1534	$42.15	$42.15	$42.20
Purchase #6	$134.81	3.191%	$139.1118	$139.11	$139.10	$139.10
Purchase #7	$153.58	13.809%	$174.7879	$174.79	$174.80	$174.80
7 purchase totals =	$1,035.94		$1,133.2874	$1,133.28	$1,133.25	$1,133.40