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	$164.91	12.297%	$185.189	$185.19	$185.20	$185.20
Purchase #2	$197.40	3.837%	$204.9742	$204.97	$204.95	$205.00
Purchase #3	$239.66	13.355%	$271.6666	$271.67	$271.65	$271.70
Purchase #4	$141.91	7.734%	$152.8853	$152.89	$152.90	$152.90
Purchase #5	$237.69	10.554%	$262.7758	$262.78	$262.80	$262.80
Purchase #6	$40.25	12.527%	$45.2921	$45.29	$45.30	$45.30
Purchase #7	$40.86	5.621%	$43.1567	$43.16	$43.15	$43.20
7 purchase totals =	$1,062.68		$1,165.9397	$1,165.95	$1,165.95	$1,166.10