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	$139.68	8.715%	$151.8531	$151.85	$151.85	$151.90
Purchase #2	$160.82	11.229%	$178.8785	$178.88	$178.90	$178.90
Purchase #3	$217.97	5.278%	$229.4745	$229.47	$229.45	$229.50
Purchase #4	$76.67	7.658%	$82.5414	$82.54	$82.55	$82.50
Purchase #5	$154.25	11.643%	$172.2093	$172.21	$172.20	$172.20
Purchase #6	$55.89	6.172%	$59.3395	$59.34	$59.35	$59.30
Purchase #7	$62.76	9.327%	$68.6136	$68.61	$68.60	$68.60
7 purchase totals =	$868.04		$942.9099	$942.90	$942.90	$942.90