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	$103.52	7.349%	$111.1277	$111.13	$111.15	$111.10
Purchase #2	$216.68	6.413%	$230.5757	$230.58	$230.60	$230.60
Purchase #3	$221.54	4.469%	$231.4406	$231.44	$231.45	$231.40
Purchase #4	$90.30	10.694%	$99.9567	$99.96	$99.95	$100.00
Purchase #5	$81.64	9.162%	$89.1199	$89.12	$89.10	$89.10
Purchase #6	$56.79	5.481%	$59.9027	$59.90	$59.90	$59.90
Purchase #7	$184.74	9.266%	$201.858	$201.86	$201.85	$201.90
7 purchase totals =	$955.21		$1,023.9813	$1,023.99	$1,024.00	$1,024.00