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	$158.49	6.299%	$168.4733	$168.47	$168.45	$168.50
Purchase #2	$177.32	7.196%	$190.0799	$190.08	$190.10	$190.10
Purchase #3	$78.96	8.526%	$85.6921	$85.69	$85.70	$85.70
Purchase #4	$53.76	5.701%	$56.8249	$56.82	$56.80	$56.80
Purchase #5	$154.88	11.431%	$172.5843	$172.58	$172.60	$172.60
Purchase #6	$238.47	12.243%	$267.6659	$267.67	$267.65	$267.70
Purchase #7	$60.73	5.352%	$63.9803	$63.98	$64.00	$64.00
7 purchase totals =	$922.61		$1,005.3007	$1,005.29	$1,005.30	$1,005.40