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	$186.60	3.353%	$192.8567	$192.86	$192.85	$192.90
Purchase #2	$157.40	12.354%	$176.8452	$176.85	$176.85	$176.80
Purchase #3	$148.92	6.717%	$158.923	$158.92	$158.90	$158.90
Purchase #4	$176.92	11.240%	$196.8058	$196.81	$196.80	$196.80
Purchase #5	$219.83	10.342%	$242.5648	$242.56	$242.55	$242.60
Purchase #6	$193.89	6.376%	$206.2524	$206.25	$206.25	$206.30
Purchase #7	$233.37	13.864%	$265.7244	$265.72	$265.70	$265.70
7 purchase totals =	$1,316.93		$1,439.9723	$1,439.97	$1,439.90	$1,440.00