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	$37.51	11.616%	$41.8672	$41.87	$41.85	$41.90
Purchase #2	$19.83	3.203%	$20.4652	$20.47	$20.45	$20.50
Purchase #3	$220.54	7.820%	$237.7862	$237.79	$237.80	$237.80
Purchase #4	$229.49	3.861%	$238.3506	$238.35	$238.35	$238.40
Purchase #5	$90.81	8.248%	$98.3	$98.30	$98.30	$98.30
Purchase #6	$102.75	6.389%	$109.3147	$109.31	$109.30	$109.30
Purchase #7	$12.32	9.711%	$13.5164	$13.52	$13.50	$13.50
7 purchase totals =	$713.25		$759.6003	$759.61	$759.55	$759.70