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	$157.95	9.173%	$172.4388	$172.44	$172.45	$172.40
Purchase #2	$77.51	8.217%	$83.879	$83.88	$83.90	$83.90
Purchase #3	$29.58	11.747%	$33.0548	$33.05	$33.05	$33.10
Purchase #4	$155.74	5.458%	$164.2403	$164.24	$164.25	$164.20
Purchase #5	$158.80	9.521%	$173.9193	$173.92	$173.90	$173.90
Purchase #6	$142.37	7.386%	$152.8854	$152.89	$152.90	$152.90
Purchase #7	$245.29	10.431%	$270.8762	$270.88	$270.90	$270.90
7 purchase totals =	$967.24		$1,051.2938	$1,051.30	$1,051.35	$1,051.30