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	$191.38	10.400%	$211.2835	$211.28	$211.30	$211.30
Purchase #2	$40.72	10.587%	$45.031	$45.03	$45.05	$45.00
Purchase #3	$235.41	8.745%	$255.9966	$256.00	$256.00	$256.00
Purchase #4	$222.57	3.691%	$230.7851	$230.79	$230.80	$230.80
Purchase #5	$41.55	9.585%	$45.5326	$45.53	$45.55	$45.50
Purchase #6	$38.97	12.593%	$43.8775	$43.88	$43.90	$43.90
Purchase #7	$59.45	9.304%	$64.9812	$64.98	$65.00	$65.00
7 purchase totals =	$830.05		$897.4875	$897.49	$897.60	$897.50