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	$243.96	13.872%	$277.8021	$277.80	$277.80	$277.80
Purchase #2	$200.88	6.522%	$213.9814	$213.98	$214.00	$214.00
Purchase #3	$114.49	3.600%	$118.6116	$118.61	$118.60	$118.60
Purchase #4	$33.90	13.270%	$38.3985	$38.40	$38.40	$38.40
Purchase #5	$142.60	7.144%	$152.7873	$152.79	$152.80	$152.80
Purchase #6	$244.99	11.798%	$273.8939	$273.89	$273.90	$273.90
Purchase #7	$63.28	4.180%	$65.9251	$65.93	$65.95	$65.90
7 purchase totals =	$1,044.10		$1,141.3999	$1,141.40	$1,141.45	$1,141.40