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	$208.46	4.834%	$218.537	$218.54	$218.55	$218.50
Purchase #2	$151.29	6.504%	$161.1299	$161.13	$161.15	$161.10
Purchase #3	$101.91	9.141%	$111.2256	$111.23	$111.25	$111.20
Purchase #4	$130.29	8.682%	$141.6018	$141.60	$141.60	$141.60
Purchase #5	$107.74	11.283%	$119.8963	$119.90	$119.90	$119.90
Purchase #6	$82.64	8.174%	$89.395	$89.40	$89.40	$89.40
Purchase #7	$62.84	6.851%	$67.1452	$67.15	$67.15	$67.10
7 purchase totals =	$845.17		$908.9308	$908.95	$909.00	$908.80