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	$128.88	13.287%	$146.0043	$146.00	$146.00	$146.00
Purchase #2	$250.91	3.191%	$258.9165	$258.92	$258.90	$258.90
Purchase #3	$198.26	12.294%	$222.6341	$222.63	$222.65	$222.60
Purchase #4	$73.84	6.442%	$78.5968	$78.60	$78.60	$78.60
Purchase #5	$105.59	10.680%	$116.867	$116.87	$116.85	$116.90
Purchase #6	$95.89	10.791%	$106.2375	$106.24	$106.25	$106.20
Purchase #7	$161.53	9.332%	$176.604	$176.60	$176.60	$176.60
7 purchase totals =	$1,014.90		$1,105.8602	$1,105.86	$1,105.85	$1,105.80