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	$88.48	12.864%	$99.8621	$99.86	$99.85	$99.90
Purchase #2	$150.91	10.640%	$166.9668	$166.97	$166.95	$167.00
Purchase #3	$249.71	9.766%	$274.0967	$274.10	$274.10	$274.10
Purchase #4	$151.68	7.351%	$162.83	$162.83	$162.85	$162.80
Purchase #5	$95.33	12.540%	$107.2844	$107.28	$107.30	$107.30
Purchase #6	$131.60	9.365%	$143.9243	$143.92	$143.90	$143.90
Purchase #7	$72.41	12.634%	$81.5583	$81.56	$81.55	$81.60
7 purchase totals =	$940.12		$1,036.5226	$1,036.52	$1,036.50	$1,036.60