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	$235.42	5.186%	$247.6289	$247.63	$247.65	$247.60
Purchase #2	$96.82	3.414%	$100.1254	$100.13	$100.15	$100.10
Purchase #3	$172.78	6.757%	$184.4547	$184.45	$184.45	$184.50
Purchase #4	$124.97	4.341%	$130.3949	$130.39	$130.40	$130.40
Purchase #5	$80.32	3.340%	$83.0027	$83.00	$83.00	$83.00
Purchase #6	$41.98	6.440%	$44.6835	$44.68	$44.70	$44.70
Purchase #7	$162.69	10.125%	$179.1624	$179.16	$179.15	$179.20
7 purchase totals =	$914.98		$969.4525	$969.44	$969.50	$969.50