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	$148.57	12.186%	$166.6747	$166.67	$166.65	$166.70
Purchase #2	$142.65	11.124%	$158.5184	$158.52	$158.50	$158.50
Purchase #3	$206.36	4.367%	$215.3717	$215.37	$215.35	$215.40
Purchase #4	$134.64	8.614%	$146.2379	$146.24	$146.25	$146.20
Purchase #5	$130.87	7.394%	$140.5465	$140.55	$140.55	$140.50
Purchase #6	$164.41	8.806%	$178.8879	$178.89	$178.90	$178.90
Purchase #7	$151.54	9.306%	$165.6423	$165.64	$165.65	$165.60
7 purchase totals =	$1,079.04		$1,171.8794	$1,171.88	$1,171.85	$1,171.80