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	$184.90	6.413%	$196.7576	$196.76	$196.75	$196.80
Purchase #2	$169.55	3.818%	$176.0234	$176.02	$176.00	$176.00
Purchase #3	$54.75	5.555%	$57.7914	$57.79	$57.80	$57.80
Purchase #4	$151.67	12.556%	$170.7137	$170.71	$170.70	$170.70
Purchase #5	$33.82	10.784%	$37.4671	$37.47	$37.45	$37.50
Purchase #6	$107.45	8.169%	$116.2276	$116.23	$116.25	$116.20
Purchase #7	$35.69	12.785%	$40.253	$40.25	$40.25	$40.30
7 purchase totals =	$737.83		$795.2338	$795.23	$795.20	$795.30