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	$154.94	3.247%	$159.9709	$159.97	$159.95	$160.00
Purchase #2	$209.34	6.164%	$222.2437	$222.24	$222.25	$222.20
Purchase #3	$178.36	5.165%	$187.5723	$187.57	$187.55	$187.60
Purchase #4	$85.94	10.583%	$95.035	$95.04	$95.05	$95.00
Purchase #5	$122.29	4.206%	$127.4335	$127.43	$127.45	$127.40
Purchase #6	$28.84	11.238%	$32.081	$32.08	$32.10	$32.10
Purchase #7	$218.63	8.533%	$237.2857	$237.29	$237.30	$237.30
7 purchase totals =	$998.34		$1,061.6221	$1,061.62	$1,061.65	$1,061.60