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	$187.27	7.232%	$200.8134	$200.81	$200.80	$200.80
Purchase #2	$136.58	10.753%	$151.2664	$151.27	$151.25	$151.30
Purchase #3	$79.80	4.618%	$83.4852	$83.49	$83.50	$83.50
Purchase #4	$62.40	11.615%	$69.6478	$69.65	$69.65	$69.60
Purchase #5	$176.89	11.146%	$196.6062	$196.61	$196.60	$196.60
Purchase #6	$62.85	5.841%	$66.5211	$66.52	$66.50	$66.50
Purchase #7	$108.31	9.774%	$118.8962	$118.90	$118.90	$118.90
7 purchase totals =	$814.10		$887.2363	$887.25	$887.20	$887.20