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	$100.61	10.469%	$111.1429	$111.14	$111.15	$111.10
Purchase #2	$236.95	5.607%	$250.2358	$250.24	$250.25	$250.20
Purchase #3	$122.99	4.794%	$128.8861	$128.89	$128.90	$128.90
Purchase #4	$132.85	8.665%	$144.3615	$144.36	$144.35	$144.40
Purchase #5	$145.55	10.709%	$161.1369	$161.14	$161.15	$161.10
Purchase #6	$81.79	10.567%	$90.4327	$90.43	$90.45	$90.40
Purchase #7	$116.36	3.781%	$120.7596	$120.76	$120.75	$120.80
7 purchase totals =	$937.10		$1,006.9555	$1,006.96	$1,007.00	$1,006.90