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	$188.92	4.188%	$196.832	$196.83	$196.85	$196.80
Purchase #2	$176.39	9.517%	$193.177	$193.18	$193.20	$193.20
Purchase #3	$125.56	4.613%	$131.3521	$131.35	$131.35	$131.40
Purchase #4	$178.91	6.189%	$189.9827	$189.98	$190.00	$190.00
Purchase #5	$139.50	12.680%	$157.1886	$157.19	$157.20	$157.20
Purchase #6	$133.40	13.800%	$151.8092	$151.81	$151.80	$151.80
Purchase #7	$218.84	10.575%	$241.9823	$241.98	$242.00	$242.00
7 purchase totals =	$1,161.52		$1,262.3239	$1,262.32	$1,262.40	$1,262.40