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	$85.81	9.814%	$94.2314	$94.23	$94.25	$94.20
Purchase #2	$118.66	12.235%	$133.1781	$133.18	$133.20	$133.20
Purchase #3	$153.89	12.380%	$172.9416	$172.94	$172.95	$172.90
Purchase #4	$211.89	7.566%	$227.9216	$227.92	$227.90	$227.90
Purchase #5	$166.25	4.209%	$173.2475	$173.25	$173.25	$173.20
Purchase #6	$58.75	6.263%	$62.4295	$62.43	$62.45	$62.40
Purchase #7	$206.40	5.428%	$217.6034	$217.60	$217.60	$217.60
7 purchase totals =	$1,001.65		$1,081.5531	$1,081.55	$1,081.60	$1,081.40