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	$153.38	11.832%	$171.5279	$171.53	$171.55	$171.50
Purchase #2	$89.31	13.117%	$101.0248	$101.02	$101.00	$101.00
Purchase #3	$9.25	11.421%	$10.3064	$10.31	$10.30	$10.30
Purchase #4	$153.50	8.328%	$166.2835	$166.28	$166.30	$166.30
Purchase #5	$10.51	13.686%	$11.9484	$11.95	$11.95	$11.90
Purchase #6	$167.68	7.700%	$180.5914	$180.59	$180.60	$180.60
Purchase #7	$96.72	3.366%	$99.9756	$99.98	$100.00	$100.00
7 purchase totals =	$680.35		$741.6580	$741.66	$741.70	$741.60