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	$17.93	9.243%	$19.5873	$19.59	$19.60	$19.60
Purchase #2	$46.66	3.414%	$48.253	$48.25	$48.25	$48.30
Purchase #3	$84.58	13.404%	$95.9171	$95.92	$95.90	$95.90
Purchase #4	$147.54	10.270%	$162.6924	$162.69	$162.70	$162.70
Purchase #5	$113.55	12.575%	$127.8289	$127.83	$127.85	$127.80
Purchase #6	$192.72	12.500%	$216.81	$216.81	$216.80	$216.80
Purchase #7	$40.32	12.133%	$45.212	$45.21	$45.20	$45.20
7 purchase totals =	$643.30		$716.3007	$716.30	$716.30	$716.30