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	$39.47	10.867%	$43.7592	$43.76	$43.75	$43.80
Purchase #2	$47.89	12.290%	$53.7757	$53.78	$53.80	$53.80
Purchase #3	$151.35	11.517%	$168.781	$168.78	$168.80	$168.80
Purchase #4	$20.85	5.680%	$22.0343	$22.03	$22.05	$22.00
Purchase #5	$54.97	3.610%	$56.9544	$56.95	$56.95	$57.00
Purchase #6	$120.98	6.351%	$128.6634	$128.66	$128.65	$128.70
Purchase #7	$83.55	5.755%	$88.3583	$88.36	$88.35	$88.40
7 purchase totals =	$519.06		$562.3263	$562.32	$562.35	$562.50