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	$250.32	3.804%	$259.8422	$259.84	$259.85	$259.80
Purchase #2	$18.90	12.706%	$21.3014	$21.30	$21.30	$21.30
Purchase #3	$75.98	13.142%	$85.9653	$85.97	$85.95	$86.00
Purchase #4	$181.82	4.418%	$189.8528	$189.85	$189.85	$189.90
Purchase #5	$98.39	6.140%	$104.4311	$104.43	$104.45	$104.40
Purchase #6	$179.78	11.195%	$199.9064	$199.91	$199.90	$199.90
Purchase #7	$177.43	7.743%	$191.1684	$191.17	$191.15	$191.20
7 purchase totals =	$982.62		$1,052.4676	$1,052.47	$1,052.45	$1,052.50