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	$241.97	8.825%	$263.3239	$263.32	$263.30	$263.30
Purchase #2	$10.48	11.737%	$11.71	$11.71	$11.70	$11.70
Purchase #3	$47.99	9.368%	$52.4857	$52.49	$52.50	$52.50
Purchase #4	$83.56	6.331%	$88.8502	$88.85	$88.85	$88.90
Purchase #5	$87.83	3.183%	$90.6256	$90.63	$90.65	$90.60
Purchase #6	$114.86	9.606%	$125.8935	$125.89	$125.90	$125.90
Purchase #7	$54.74	13.758%	$62.2711	$62.27	$62.25	$62.30
7 purchase totals =	$641.43		$695.1600	$695.16	$695.15	$695.20