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	$116.41	8.436%	$126.2303	$126.23	$126.25	$126.20
Purchase #2	$17.73	6.654%	$18.9098	$18.91	$18.90	$18.90
Purchase #3	$138.69	4.491%	$144.9186	$144.92	$144.90	$144.90
Purchase #4	$78.79	13.558%	$89.4723	$89.47	$89.45	$89.50
Purchase #5	$63.93	5.503%	$67.4481	$67.45	$67.45	$67.40
Purchase #6	$154.51	3.119%	$159.3292	$159.33	$159.35	$159.30
Purchase #7	$147.76	3.762%	$153.3187	$153.32	$153.30	$153.30
7 purchase totals =	$717.82		$759.6270	$759.63	$759.60	$759.50