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	$60.77	10.870%	$67.3757	$67.38	$67.40	$67.40
Purchase #2	$95.37	5.636%	$100.7451	$100.75	$100.75	$100.70
Purchase #3	$54.25	4.729%	$56.8155	$56.82	$56.80	$56.80
Purchase #4	$172.50	5.384%	$181.7874	$181.79	$181.80	$181.80
Purchase #5	$224.27	8.717%	$243.8196	$243.82	$243.80	$243.80
Purchase #6	$195.47	4.416%	$204.102	$204.10	$204.10	$204.10
Purchase #7	$186.94	10.629%	$206.8099	$206.81	$206.80	$206.80
7 purchase totals =	$989.57		$1,061.4552	$1,061.47	$1,061.45	$1,061.40