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	$111.94	10.323%	$123.4956	$123.50	$123.50	$123.50
Purchase #2	$122.34	7.444%	$131.447	$131.45	$131.45	$131.40
Purchase #3	$45.86	7.232%	$49.1766	$49.18	$49.20	$49.20
Purchase #4	$101.82	13.579%	$115.6461	$115.65	$115.65	$115.60
Purchase #5	$157.34	5.798%	$166.4626	$166.46	$166.45	$166.50
Purchase #6	$143.90	11.300%	$160.1607	$160.16	$160.15	$160.20
Purchase #7	$220.72	11.370%	$245.8159	$245.82	$245.80	$245.80
7 purchase totals =	$903.92		$992.2045	$992.22	$992.20	$992.20