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	$222.63	10.290%	$245.5386	$245.54	$245.55	$245.50
Purchase #2	$135.27	8.320%	$146.5245	$146.52	$146.50	$146.50
Purchase #3	$30.94	9.540%	$33.8917	$33.89	$33.90	$33.90
Purchase #4	$157.98	9.328%	$172.7164	$172.72	$172.70	$172.70
Purchase #5	$207.97	7.854%	$224.304	$224.30	$224.30	$224.30
Purchase #6	$109.81	11.386%	$122.313	$122.31	$122.30	$122.30
Purchase #7	$142.81	10.807%	$158.2435	$158.24	$158.25	$158.20
7 purchase totals =	$1,007.41		$1,103.5317	$1,103.52	$1,103.50	$1,103.40