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	$111.40	10.280%	$122.8519	$122.85	$122.85	$122.90
Purchase #2	$65.51	9.621%	$71.8127	$71.81	$71.80	$71.80
Purchase #3	$195.99	10.831%	$217.2177	$217.22	$217.20	$217.20
Purchase #4	$5.95	8.874%	$6.478	$6.48	$6.50	$6.50
Purchase #5	$21.77	3.734%	$22.5829	$22.58	$22.60	$22.60
Purchase #6	$90.89	10.511%	$100.4434	$100.44	$100.45	$100.40
Purchase #7	$62.78	9.761%	$68.908	$68.91	$68.90	$68.90
7 purchase totals =	$554.29		$610.2946	$610.29	$610.30	$610.30