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	$217.31	13.558%	$246.7729	$246.77	$246.75	$246.80
Purchase #2	$95.96	8.852%	$104.4544	$104.45	$104.45	$104.50
Purchase #3	$180.86	6.378%	$192.3953	$192.40	$192.40	$192.40
Purchase #4	$86.92	13.745%	$98.8672	$98.87	$98.85	$98.90
Purchase #5	$75.38	9.261%	$82.3609	$82.36	$82.35	$82.40
Purchase #6	$174.82	11.664%	$195.211	$195.21	$195.20	$195.20
Purchase #7	$79.47	3.844%	$82.5248	$82.52	$82.50	$82.50
7 purchase totals =	$910.72		$1,002.5865	$1,002.58	$1,002.50	$1,002.70