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	$210.47	12.601%	$236.9913	$236.99	$237.00	$237.00
Purchase #2	$59.38	13.543%	$67.4218	$67.42	$67.40	$67.40
Purchase #3	$78.88	8.873%	$85.879	$85.88	$85.90	$85.90
Purchase #4	$12.97	10.152%	$14.2867	$14.29	$14.30	$14.30
Purchase #5	$228.55	11.699%	$255.2881	$255.29	$255.30	$255.30
Purchase #6	$102.67	8.324%	$111.2163	$111.22	$111.20	$111.20
Purchase #7	$178.59	6.401%	$190.0215	$190.02	$190.00	$190.00
7 purchase totals =	$871.51		$961.1047	$961.11	$961.10	$961.10