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	$128.57	11.252%	$143.0367	$143.04	$143.05	$143.00
Purchase #2	$247.47	7.690%	$266.5004	$266.50	$266.50	$266.50
Purchase #3	$38.51	6.156%	$40.8807	$40.88	$40.90	$40.90
Purchase #4	$152.86	4.356%	$159.5186	$159.52	$159.50	$159.50
Purchase #5	$21.79	11.440%	$24.2828	$24.28	$24.30	$24.30
Purchase #6	$57.59	12.182%	$64.6056	$64.61	$64.60	$64.60
Purchase #7	$194.44	7.173%	$208.3872	$208.39	$208.40	$208.40
7 purchase totals =	$841.23		$907.2120	$907.22	$907.25	$907.20