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	$164.60	11.531%	$183.58	$183.58	$183.60	$183.60
Purchase #2	$30.45	3.712%	$31.5803	$31.58	$31.60	$31.60
Purchase #3	$115.29	8.164%	$124.7023	$124.70	$124.70	$124.70
Purchase #4	$240.63	6.354%	$255.9196	$255.92	$255.90	$255.90
Purchase #5	$119.41	9.823%	$131.1396	$131.14	$131.15	$131.10
Purchase #6	$96.71	5.105%	$101.647	$101.65	$101.65	$101.60
Purchase #7	$104.98	4.341%	$109.5372	$109.54	$109.55	$109.50
7 purchase totals =	$872.07		$938.1060	$938.11	$938.15	$938.00