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	$142.69	11.375%	$158.921	$158.92	$158.90	$158.90
Purchase #2	$212.29	10.473%	$234.5231	$234.52	$234.50	$234.50
Purchase #3	$54.81	7.311%	$58.8172	$58.82	$58.80	$58.80
Purchase #4	$39.92	3.370%	$41.2653	$41.27	$41.25	$41.30
Purchase #5	$91.35	13.314%	$103.5123	$103.51	$103.50	$103.50
Purchase #6	$38.28	6.250%	$40.6725	$40.67	$40.65	$40.70
Purchase #7	$235.73	5.230%	$248.0587	$248.06	$248.05	$248.10
7 purchase totals =	$815.07		$885.7701	$885.77	$885.65	$885.80