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	$102.67	8.700%	$111.6023	$111.60	$111.60	$111.60
Purchase #2	$17.56	12.704%	$19.7908	$19.79	$19.80	$19.80
Purchase #3	$87.54	6.215%	$92.9806	$92.98	$93.00	$93.00
Purchase #4	$18.99	6.655%	$20.2538	$20.25	$20.25	$20.30
Purchase #5	$75.64	4.211%	$78.8252	$78.83	$78.85	$78.80
Purchase #6	$174.31	13.654%	$198.1103	$198.11	$198.10	$198.10
Purchase #7	$51.98	9.539%	$56.9384	$56.94	$56.95	$56.90
7 purchase totals =	$528.69		$578.5014	$578.50	$578.55	$578.50