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	$59.33	7.585%	$63.8302	$63.83	$63.85	$63.80
Purchase #2	$39.63	13.613%	$45.0248	$45.02	$45.00	$45.00
Purchase #3	$53.98	3.507%	$55.8731	$55.87	$55.85	$55.90
Purchase #4	$9.98	8.389%	$10.8172	$10.82	$10.80	$10.80
Purchase #5	$98.97	4.201%	$103.1277	$103.13	$103.15	$103.10
Purchase #6	$236.44	12.530%	$266.0659	$266.07	$266.05	$266.10
Purchase #7	$11.79	9.109%	$12.864	$12.86	$12.85	$12.90
7 purchase totals =	$510.12		$557.6029	$557.60	$557.55	$557.60