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	$246.69	13.404%	$279.7563	$279.76	$279.75	$279.80
Purchase #2	$11.93	5.503%	$12.5865	$12.59	$12.60	$12.60
Purchase #3	$46.47	13.144%	$52.578	$52.58	$52.60	$52.60
Purchase #4	$184.31	13.566%	$209.3135	$209.31	$209.30	$209.30
Purchase #5	$225.92	7.826%	$243.6005	$243.60	$243.60	$243.60
Purchase #6	$193.85	12.673%	$218.4166	$218.42	$218.40	$218.40
Purchase #7	$190.39	8.716%	$206.9844	$206.98	$207.00	$207.00
7 purchase totals =	$1,099.56		$1,223.2358	$1,223.24	$1,223.25	$1,223.30