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	$103.76	12.504%	$116.7342	$116.73	$116.75	$116.70
Purchase #2	$99.60	4.321%	$103.9037	$103.90	$103.90	$103.90
Purchase #3	$152.82	13.383%	$173.2719	$173.27	$173.25	$173.30
Purchase #4	$246.38	5.229%	$259.2632	$259.26	$259.25	$259.30
Purchase #5	$207.51	5.220%	$218.342	$218.34	$218.35	$218.30
Purchase #6	$179.38	8.439%	$194.5179	$194.52	$194.50	$194.50
Purchase #7	$104.88	6.190%	$111.3721	$111.37	$111.35	$111.40
7 purchase totals =	$1,094.33		$1,177.4050	$1,177.39	$1,177.35	$1,177.40