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	$105.66	5.836%	$111.8263	$111.83	$111.85	$111.80
Purchase #2	$242.37	13.514%	$275.1239	$275.12	$275.10	$275.10
Purchase #3	$57.80	8.786%	$62.8783	$62.88	$62.90	$62.90
Purchase #4	$158.54	8.497%	$172.0111	$172.01	$172.00	$172.00
Purchase #5	$147.40	7.195%	$158.0054	$158.01	$158.00	$158.00
Purchase #6	$247.75	4.320%	$258.4528	$258.45	$258.45	$258.50
Purchase #7	$67.86	7.439%	$72.9081	$72.91	$72.90	$72.90
7 purchase totals =	$1,027.38		$1,111.2059	$1,111.21	$1,111.20	$1,111.20