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	$163.43	4.315%	$170.482	$170.48	$170.50	$170.50
Purchase #2	$152.80	9.345%	$167.0792	$167.08	$167.10	$167.10
Purchase #3	$131.35	11.348%	$146.2556	$146.26	$146.25	$146.30
Purchase #4	$217.34	9.709%	$238.4415	$238.44	$238.45	$238.40
Purchase #5	$69.98	3.864%	$72.684	$72.68	$72.70	$72.70
Purchase #6	$204.61	11.728%	$228.6067	$228.61	$228.60	$228.60
Purchase #7	$84.51	5.779%	$89.3938	$89.39	$89.40	$89.40
7 purchase totals =	$1,024.02		$1,112.9428	$1,112.94	$1,113.00	$1,113.00