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	$67.37	8.827%	$73.3167	$73.32	$73.30	$73.30
Purchase #2	$59.67	3.404%	$61.7012	$61.70	$61.70	$61.70
Purchase #3	$134.56	3.186%	$138.8471	$138.85	$138.85	$138.80
Purchase #4	$85.79	11.753%	$95.8729	$95.87	$95.85	$95.90
Purchase #5	$125.52	9.501%	$137.4457	$137.45	$137.45	$137.40
Purchase #6	$44.83	12.131%	$50.2683	$50.27	$50.25	$50.30
Purchase #7	$184.98	10.189%	$203.8276	$203.83	$203.85	$203.80
7 purchase totals =	$702.72		$761.2795	$761.29	$761.25	$761.20