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	$163.56	13.118%	$185.0158	$185.02	$185.00	$185.00
Purchase #2	$108.33	10.175%	$119.3526	$119.35	$119.35	$119.40
Purchase #3	$132.54	3.643%	$137.3684	$137.37	$137.35	$137.40
Purchase #4	$18.58	12.371%	$20.8785	$20.88	$20.90	$20.90
Purchase #5	$108.85	8.519%	$118.1229	$118.12	$118.10	$118.10
Purchase #6	$17.85	12.611%	$20.1011	$20.10	$20.10	$20.10
Purchase #7	$176.42	4.677%	$184.6712	$184.67	$184.65	$184.70
7 purchase totals =	$726.13		$785.5105	$785.51	$785.45	$785.60