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	$158.93	12.850%	$179.3525	$179.35	$179.35	$179.40
Purchase #2	$204.89	7.328%	$219.9043	$219.90	$219.90	$219.90
Purchase #3	$159.73	3.247%	$164.9164	$164.92	$164.90	$164.90
Purchase #4	$20.90	5.390%	$22.0265	$22.03	$22.05	$22.00
Purchase #5	$36.55	10.187%	$40.2733	$40.27	$40.25	$40.30
Purchase #6	$156.51	3.556%	$162.0755	$162.08	$162.10	$162.10
Purchase #7	$162.33	10.289%	$179.0321	$179.03	$179.05	$179.00
7 purchase totals =	$899.84		$967.5806	$967.58	$967.60	$967.60