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	$64.91	4.222%	$67.6505	$67.65	$67.65	$67.70
Purchase #2	$98.86	12.462%	$111.1799	$111.18	$111.20	$111.20
Purchase #3	$139.98	3.698%	$145.1565	$145.16	$145.15	$145.20
Purchase #4	$33.50	12.195%	$37.5853	$37.59	$37.60	$37.60
Purchase #5	$137.41	5.325%	$144.7271	$144.73	$144.75	$144.70
Purchase #6	$7.90	4.756%	$8.2757	$8.28	$8.30	$8.30
Purchase #7	$93.84	6.753%	$100.177	$100.18	$100.20	$100.20
7 purchase totals =	$576.40		$614.7520	$614.77	$614.85	$614.90