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	$25.67	6.480%	$27.3334	$27.33	$27.35	$27.30
Purchase #2	$238.31	7.760%	$256.8029	$256.80	$256.80	$256.80
Purchase #3	$74.65	5.170%	$78.5094	$78.51	$78.50	$78.50
Purchase #4	$166.35	5.527%	$175.5442	$175.54	$175.55	$175.50
Purchase #5	$220.45	9.201%	$240.7336	$240.73	$240.75	$240.70
Purchase #6	$179.92	6.671%	$191.9225	$191.92	$191.90	$191.90
Purchase #7	$130.52	11.292%	$145.2583	$145.26	$145.25	$145.30
7 purchase totals =	$1,035.87		$1,116.1043	$1,116.09	$1,116.10	$1,116.00