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	$44.61	4.706%	$46.7093	$46.71	$46.70	$46.70
Purchase #2	$167.88	13.352%	$190.2953	$190.30	$190.30	$190.30
Purchase #3	$180.35	5.524%	$190.3125	$190.31	$190.30	$190.30
Purchase #4	$162.75	3.232%	$168.0101	$168.01	$168.00	$168.00
Purchase #5	$32.28	6.194%	$34.2794	$34.28	$34.30	$34.30
Purchase #6	$37.36	8.395%	$40.4964	$40.50	$40.50	$40.50
Purchase #7	$101.60	10.807%	$112.5799	$112.58	$112.60	$112.60
7 purchase totals =	$726.83		$782.6829	$782.69	$782.70	$782.70