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	$132.74	4.830%	$139.1513	$139.15	$139.15	$139.20
Purchase #2	$203.97	3.138%	$210.3706	$210.37	$210.35	$210.40
Purchase #3	$143.51	4.360%	$149.767	$149.77	$149.75	$149.80
Purchase #4	$95.32	10.550%	$105.3763	$105.38	$105.40	$105.40
Purchase #5	$103.59	13.273%	$117.3395	$117.34	$117.35	$117.30
Purchase #6	$173.39	6.837%	$185.2447	$185.24	$185.25	$185.20
Purchase #7	$128.56	8.453%	$139.4272	$139.43	$139.45	$139.40
7 purchase totals =	$981.08		$1,046.6766	$1,046.68	$1,046.70	$1,046.70