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	$148.95	6.222%	$158.2177	$158.22	$158.20	$158.20
Purchase #2	$128.62	8.771%	$139.9013	$139.90	$139.90	$139.90
Purchase #3	$66.90	9.447%	$73.22	$73.22	$73.20	$73.20
Purchase #4	$239.88	13.168%	$271.4674	$271.47	$271.45	$271.50
Purchase #5	$246.62	3.424%	$255.0643	$255.06	$255.05	$255.10
Purchase #6	$33.48	12.544%	$37.6797	$37.68	$37.70	$37.70
Purchase #7	$88.27	8.173%	$95.4843	$95.48	$95.50	$95.50
7 purchase totals =	$952.72		$1,031.0347	$1,031.03	$1,031.00	$1,031.10