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	$191.66	3.612%	$198.5828	$198.58	$198.60	$198.60
Purchase #2	$205.58	13.461%	$233.2531	$233.25	$233.25	$233.30
Purchase #3	$96.89	13.217%	$109.696	$109.70	$109.70	$109.70
Purchase #4	$179.70	6.147%	$190.7462	$190.75	$190.75	$190.70
Purchase #5	$51.93	10.593%	$57.4309	$57.43	$57.45	$57.40
Purchase #6	$64.83	10.271%	$71.4887	$71.49	$71.50	$71.50
Purchase #7	$85.97	3.257%	$88.77	$88.77	$88.75	$88.80
7 purchase totals =	$876.56		$949.9677	$949.97	$950.00	$950.00