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	$188.56	10.388%	$208.1476	$208.15	$208.15	$208.10
Purchase #2	$61.84	5.140%	$65.0186	$65.02	$65.00	$65.00
Purchase #3	$131.64	8.312%	$142.5819	$142.58	$142.60	$142.60
Purchase #4	$17.33	6.518%	$18.4596	$18.46	$18.45	$18.50
Purchase #5	$47.39	5.857%	$50.1656	$50.17	$50.15	$50.20
Purchase #6	$210.94	6.296%	$224.2208	$224.22	$224.20	$224.20
Purchase #7	$169.71	8.315%	$183.8214	$183.82	$183.80	$183.80
7 purchase totals =	$827.41		$892.4155	$892.42	$892.35	$892.40