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	$163.30	10.308%	$180.133	$180.13	$180.15	$180.10
Purchase #2	$206.87	11.604%	$230.8752	$230.88	$230.90	$230.90
Purchase #3	$102.85	6.607%	$109.6453	$109.65	$109.65	$109.60
Purchase #4	$182.57	4.795%	$191.3242	$191.32	$191.30	$191.30
Purchase #5	$31.73	4.710%	$33.2245	$33.22	$33.20	$33.20
Purchase #6	$175.84	9.204%	$192.0243	$192.02	$192.00	$192.00
Purchase #7	$222.73	5.447%	$234.8621	$234.86	$234.85	$234.90
7 purchase totals =	$1,085.89		$1,172.0886	$1,172.08	$1,172.05	$1,172.00