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	$160.58	7.249%	$172.2204	$172.22	$172.20	$172.20
Purchase #2	$7.40	10.406%	$8.17	$8.17	$8.15	$8.20
Purchase #3	$130.94	6.757%	$139.7876	$139.79	$139.80	$139.80
Purchase #4	$92.75	13.637%	$105.3983	$105.40	$105.40	$105.40
Purchase #5	$38.38	7.706%	$41.3376	$41.34	$41.35	$41.30
Purchase #6	$154.46	11.760%	$172.6245	$172.62	$172.60	$172.60
Purchase #7	$135.29	4.777%	$141.7528	$141.75	$141.75	$141.80
7 purchase totals =	$719.80		$781.2912	$781.29	$781.25	$781.30