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	$156.65	13.782%	$178.2395	$178.24	$178.25	$178.20
Purchase #2	$154.31	3.352%	$159.4825	$159.48	$159.50	$159.50
Purchase #3	$82.40	9.665%	$90.364	$90.36	$90.35	$90.40
Purchase #4	$214.84	8.517%	$233.1379	$233.14	$233.15	$233.10
Purchase #5	$159.71	3.224%	$164.8591	$164.86	$164.85	$164.90
Purchase #6	$197.98	11.298%	$220.3478	$220.35	$220.35	$220.30
Purchase #7	$13.66	3.697%	$14.165	$14.17	$14.15	$14.20
7 purchase totals =	$979.55		$1,060.5958	$1,060.60	$1,060.60	$1,060.60