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	$65.46	3.614%	$67.8257	$67.83	$67.85	$67.80
Purchase #2	$99.71	11.676%	$111.3521	$111.35	$111.35	$111.40
Purchase #3	$153.60	8.492%	$166.6437	$166.64	$166.65	$166.60
Purchase #4	$105.47	13.102%	$119.2887	$119.29	$119.30	$119.30
Purchase #5	$242.33	3.205%	$250.0967	$250.10	$250.10	$250.10
Purchase #6	$168.65	4.672%	$176.5293	$176.53	$176.55	$176.50
Purchase #7	$124.74	9.316%	$136.3608	$136.36	$136.35	$136.40
7 purchase totals =	$959.96		$1,028.0970	$1,028.10	$1,028.15	$1,028.10