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	$166.41	12.579%	$187.3427	$187.34	$187.35	$187.30
Purchase #2	$227.48	4.412%	$237.5164	$237.52	$237.50	$237.50
Purchase #3	$207.32	4.220%	$216.0689	$216.07	$216.05	$216.10
Purchase #4	$134.67	3.869%	$139.8804	$139.88	$139.90	$139.90
Purchase #5	$112.38	9.603%	$123.1719	$123.17	$123.15	$123.20
Purchase #6	$29.35	11.388%	$32.6924	$32.69	$32.70	$32.70
Purchase #7	$156.36	6.782%	$166.9643	$166.96	$166.95	$167.00
7 purchase totals =	$1,033.97		$1,103.6370	$1,103.63	$1,103.60	$1,103.70