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	$103.87	9.647%	$113.8903	$113.89	$113.90	$113.90
Purchase #2	$89.82	5.250%	$94.5356	$94.54	$94.55	$94.50
Purchase #3	$127.60	13.471%	$144.789	$144.79	$144.80	$144.80
Purchase #4	$226.63	6.301%	$240.91	$240.91	$240.90	$240.90
Purchase #5	$170.74	12.200%	$191.5703	$191.57	$191.55	$191.60
Purchase #6	$197.98	3.507%	$204.9232	$204.92	$204.90	$204.90
Purchase #7	$127.58	11.504%	$142.2568	$142.26	$142.25	$142.30
7 purchase totals =	$1,044.22		$1,132.8752	$1,132.88	$1,132.85	$1,132.90