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	$231.54	4.435%	$241.8088	$241.81	$241.80	$241.80
Purchase #2	$78.69	10.308%	$86.8014	$86.80	$86.80	$86.80
Purchase #3	$214.52	12.859%	$242.1051	$242.11	$242.10	$242.10
Purchase #4	$17.88	13.323%	$20.2622	$20.26	$20.25	$20.30
Purchase #5	$209.82	9.561%	$229.8809	$229.88	$229.90	$229.90
Purchase #6	$224.92	10.851%	$249.3261	$249.33	$249.35	$249.30
Purchase #7	$160.59	7.264%	$172.2553	$172.26	$172.25	$172.30
7 purchase totals =	$1,137.96		$1,242.4398	$1,242.45	$1,242.45	$1,242.50