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	$53.55	3.517%	$55.4334	$55.43	$55.45	$55.40
Purchase #2	$108.45	7.773%	$116.8798	$116.88	$116.90	$116.90
Purchase #3	$126.62	12.267%	$142.1525	$142.15	$142.15	$142.20
Purchase #4	$93.73	12.713%	$105.6459	$105.65	$105.65	$105.60
Purchase #5	$31.48	3.842%	$32.6895	$32.69	$32.70	$32.70
Purchase #6	$148.87	3.646%	$154.2978	$154.30	$154.30	$154.30
Purchase #7	$18.40	11.125%	$20.447	$20.45	$20.45	$20.40
7 purchase totals =	$581.10		$627.5459	$627.55	$627.60	$627.50