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	$34.59	3.221%	$35.7041	$35.70	$35.70	$35.70
Purchase #2	$232.67	9.838%	$255.5601	$255.56	$255.55	$255.60
Purchase #3	$149.45	9.725%	$163.984	$163.98	$164.00	$164.00
Purchase #4	$31.72	12.613%	$35.7208	$35.72	$35.70	$35.70
Purchase #5	$57.25	8.162%	$61.9227	$61.92	$61.90	$61.90
Purchase #6	$17.85	12.224%	$20.032	$20.03	$20.05	$20.00
Purchase #7	$41.91	11.159%	$46.5867	$46.59	$46.60	$46.60
7 purchase totals =	$565.44		$619.5104	$619.50	$619.50	$619.50