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	$158.90	4.319%	$165.7629	$165.76	$165.75	$165.80
Purchase #2	$144.36	9.566%	$158.1695	$158.17	$158.15	$158.20
Purchase #3	$20.35	4.564%	$21.2788	$21.28	$21.30	$21.30
Purchase #4	$141.48	10.525%	$156.3708	$156.37	$156.35	$156.40
Purchase #5	$234.88	13.833%	$267.371	$267.37	$267.35	$267.40
Purchase #6	$130.88	7.161%	$140.2523	$140.25	$140.25	$140.30
Purchase #7	$139.40	8.550%	$151.3187	$151.32	$151.30	$151.30
7 purchase totals =	$970.25		$1,060.5240	$1,060.52	$1,060.45	$1,060.70