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	$83.89	13.755%	$95.4291	$95.43	$95.45	$95.40
Purchase #2	$171.32	13.786%	$194.9382	$194.94	$194.95	$194.90
Purchase #3	$118.86	7.284%	$127.5178	$127.52	$127.50	$127.50
Purchase #4	$124.33	6.579%	$132.5097	$132.51	$132.50	$132.50
Purchase #5	$34.76	4.368%	$36.2783	$36.28	$36.30	$36.30
Purchase #6	$195.97	7.333%	$210.3405	$210.34	$210.35	$210.30
Purchase #7	$83.61	10.143%	$92.0906	$92.09	$92.10	$92.10
7 purchase totals =	$812.74		$889.1042	$889.11	$889.15	$889.00