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	$31.82	4.739%	$33.3279	$33.33	$33.35	$33.30
Purchase #2	$172.59	12.450%	$194.0775	$194.08	$194.10	$194.10
Purchase #3	$63.92	13.484%	$72.539	$72.54	$72.55	$72.50
Purchase #4	$234.62	6.351%	$249.5207	$249.52	$249.50	$249.50
Purchase #5	$19.48	3.847%	$20.2294	$20.23	$20.25	$20.20
Purchase #6	$95.33	11.797%	$106.5761	$106.58	$106.60	$106.60
Purchase #7	$116.83	13.830%	$132.9876	$132.99	$133.00	$133.00
7 purchase totals =	$734.59		$809.2582	$809.27	$809.35	$809.20