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	$121.75	5.615%	$128.5863	$128.59	$128.60	$128.60
Purchase #2	$162.59	7.156%	$174.2249	$174.22	$174.20	$174.20
Purchase #3	$179.84	13.509%	$204.1346	$204.13	$204.15	$204.10
Purchase #4	$142.83	7.526%	$153.5794	$153.58	$153.60	$153.60
Purchase #5	$64.95	8.539%	$70.4961	$70.50	$70.50	$70.50
Purchase #6	$179.46	4.471%	$187.4837	$187.48	$187.50	$187.50
Purchase #7	$89.87	12.700%	$101.2835	$101.28	$101.30	$101.30
7 purchase totals =	$941.29		$1,019.7885	$1,019.78	$1,019.85	$1,019.80