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	$64.98	12.287%	$72.9641	$72.96	$72.95	$73.00
Purchase #2	$114.78	7.594%	$123.4964	$123.50	$123.50	$123.50
Purchase #3	$94.70	5.590%	$99.9937	$99.99	$100.00	$100.00
Purchase #4	$107.40	8.292%	$116.3056	$116.31	$116.30	$116.30
Purchase #5	$95.39	6.635%	$101.7191	$101.72	$101.70	$101.70
Purchase #6	$134.88	11.311%	$150.1363	$150.14	$150.15	$150.10
Purchase #7	$41.92	3.680%	$43.4627	$43.46	$43.45	$43.50
7 purchase totals =	$654.05		$708.0779	$708.08	$708.05	$708.10