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	$165.56	9.846%	$181.861	$181.86	$181.85	$181.90
Purchase #2	$94.39	9.220%	$103.0928	$103.09	$103.10	$103.10
Purchase #3	$130.68	12.366%	$146.8399	$146.84	$146.85	$146.80
Purchase #4	$51.85	12.516%	$58.3395	$58.34	$58.35	$58.30
Purchase #5	$232.41	10.104%	$255.8927	$255.89	$255.90	$255.90
Purchase #6	$143.28	6.463%	$152.5402	$152.54	$152.55	$152.50
Purchase #7	$58.31	9.104%	$63.6185	$63.62	$63.60	$63.60
7 purchase totals =	$876.48		$962.1846	$962.18	$962.20	$962.10