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	$179.39	11.332%	$199.7185	$199.72	$199.70	$199.70
Purchase #2	$91.97	7.621%	$98.979	$98.98	$99.00	$99.00
Purchase #3	$179.95	3.109%	$185.5446	$185.54	$185.55	$185.50
Purchase #4	$215.32	8.766%	$234.195	$234.20	$234.20	$234.20
Purchase #5	$87.71	12.874%	$99.0018	$99.00	$99.00	$99.00
Purchase #6	$24.75	4.341%	$25.8244	$25.82	$25.80	$25.80
Purchase #7	$170.52	3.348%	$176.229	$176.23	$176.25	$176.20
7 purchase totals =	$949.61		$1,019.4923	$1,019.49	$1,019.50	$1,019.40