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	$227.72	7.264%	$244.2616	$244.26	$244.25	$244.30
Purchase #2	$15.81	6.766%	$16.8797	$16.88	$16.90	$16.90
Purchase #3	$154.78	11.745%	$172.9589	$172.96	$172.95	$173.00
Purchase #4	$82.80	9.300%	$90.5004	$90.50	$90.50	$90.50
Purchase #5	$186.56	11.275%	$207.5946	$207.59	$207.60	$207.60
Purchase #6	$109.81	3.674%	$113.8444	$113.84	$113.85	$113.80
Purchase #7	$186.28	12.603%	$209.7569	$209.76	$209.75	$209.80
7 purchase totals =	$963.76		$1,055.7965	$1,055.79	$1,055.80	$1,055.90