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	$9.72	11.249%	$10.8134	$10.81	$10.80	$10.80
Purchase #2	$214.68	12.709%	$241.9637	$241.96	$241.95	$242.00
Purchase #3	$34.98	10.363%	$38.605	$38.61	$38.60	$38.60
Purchase #4	$85.33	4.415%	$89.0973	$89.10	$89.10	$89.10
Purchase #5	$120.73	5.431%	$127.2868	$127.29	$127.30	$127.30
Purchase #6	$210.69	11.343%	$234.5886	$234.59	$234.60	$234.60
Purchase #7	$153.73	4.232%	$160.2359	$160.24	$160.25	$160.20
7 purchase totals =	$829.86		$902.5907	$902.60	$902.60	$902.60