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	$228.29	4.643%	$238.8895	$238.89	$238.90	$238.90
Purchase #2	$105.43	3.808%	$109.4448	$109.44	$109.45	$109.40
Purchase #3	$142.76	4.693%	$149.4597	$149.46	$149.45	$149.50
Purchase #4	$164.76	9.493%	$180.4007	$180.40	$180.40	$180.40
Purchase #5	$31.90	5.692%	$33.7157	$33.72	$33.70	$33.70
Purchase #6	$237.94	6.418%	$253.211	$253.21	$253.20	$253.20
Purchase #7	$170.74	3.608%	$176.9003	$176.90	$176.90	$176.90
7 purchase totals =	$1,081.82		$1,142.0217	$1,142.02	$1,142.00	$1,142.00