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	$146.87	9.131%	$160.2807	$160.28	$160.30	$160.30
Purchase #2	$34.64	5.316%	$36.4815	$36.48	$36.50	$36.50
Purchase #3	$86.63	6.315%	$92.1007	$92.10	$92.10	$92.10
Purchase #4	$203.76	6.578%	$217.1633	$217.16	$217.15	$217.20
Purchase #5	$103.80	7.706%	$111.7988	$111.80	$111.80	$111.80
Purchase #6	$42.44	7.135%	$45.4681	$45.47	$45.45	$45.50
Purchase #7	$32.99	12.632%	$37.1573	$37.16	$37.15	$37.20
7 purchase totals =	$651.13		$700.4504	$700.45	$700.45	$700.60