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	$72.42	13.671%	$82.3205	$82.32	$82.30	$82.30
Purchase #2	$32.79	11.495%	$36.5592	$36.56	$36.55	$36.60
Purchase #3	$84.44	5.317%	$88.9297	$88.93	$88.95	$88.90
Purchase #4	$194.92	13.524%	$221.281	$221.28	$221.30	$221.30
Purchase #5	$111.51	13.513%	$126.5783	$126.58	$126.60	$126.60
Purchase #6	$232.40	10.566%	$256.9554	$256.96	$256.95	$257.00
Purchase #7	$247.69	3.574%	$256.5424	$256.54	$256.55	$256.50
7 purchase totals =	$976.17		$1,069.1665	$1,069.17	$1,069.20	$1,069.20