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	$181.69	12.614%	$204.6084	$204.61	$204.60	$204.60
Purchase #2	$194.56	11.429%	$216.7963	$216.80	$216.80	$216.80
Purchase #3	$39.71	4.611%	$41.541	$41.54	$41.55	$41.50
Purchase #4	$105.74	5.298%	$111.3421	$111.34	$111.35	$111.30
Purchase #5	$39.95	12.524%	$44.9533	$44.95	$44.95	$45.00
Purchase #6	$192.86	8.433%	$209.1239	$209.12	$209.10	$209.10
Purchase #7	$157.81	9.195%	$172.3206	$172.32	$172.30	$172.30
7 purchase totals =	$912.32		$1,000.6856	$1,000.68	$1,000.65	$1,000.60