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	$118.86	9.353%	$129.977	$129.98	$130.00	$130.00
Purchase #2	$82.79	9.549%	$90.6956	$90.70	$90.70	$90.70
Purchase #3	$104.40	9.714%	$114.5414	$114.54	$114.55	$114.50
Purchase #4	$209.54	11.329%	$233.2788	$233.28	$233.30	$233.30
Purchase #5	$240.27	10.855%	$266.3513	$266.35	$266.35	$266.40
Purchase #6	$10.62	9.231%	$11.6003	$11.60	$11.60	$11.60
Purchase #7	$105.34	4.131%	$109.6916	$109.69	$109.70	$109.70
7 purchase totals =	$871.82		$956.1360	$956.14	$956.20	$956.20