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	$242.53	8.294%	$262.6454	$262.65	$262.65	$262.60
Purchase #2	$13.50	6.380%	$14.3613	$14.36	$14.35	$14.40
Purchase #3	$99.31	12.647%	$111.8697	$111.87	$111.85	$111.90
Purchase #4	$124.51	11.232%	$138.495	$138.50	$138.50	$138.50
Purchase #5	$49.47	8.564%	$53.7066	$53.71	$53.70	$53.70
Purchase #6	$116.94	5.479%	$123.3471	$123.35	$123.35	$123.30
Purchase #7	$87.63	12.641%	$98.7073	$98.71	$98.70	$98.70
7 purchase totals =	$733.89		$803.1324	$803.15	$803.10	$803.10