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	$132.66	7.736%	$142.9226	$142.92	$142.90	$142.90
Purchase #2	$63.52	5.395%	$66.9469	$66.95	$66.95	$66.90
Purchase #3	$181.28	3.136%	$186.9649	$186.96	$186.95	$187.00
Purchase #4	$139.93	3.525%	$144.8625	$144.86	$144.85	$144.90
Purchase #5	$64.70	3.361%	$66.8746	$66.87	$66.85	$66.90
Purchase #6	$73.91	10.860%	$81.9366	$81.94	$81.95	$81.90
Purchase #7	$41.47	9.220%	$45.2935	$45.29	$45.30	$45.30
7 purchase totals =	$697.47		$735.8016	$735.79	$735.75	$735.80