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	$13.90	4.548%	$14.5322	$14.53	$14.55	$14.50
Purchase #2	$107.66	10.405%	$118.862	$118.86	$118.85	$118.90
Purchase #3	$103.61	8.355%	$112.2666	$112.27	$112.25	$112.30
Purchase #4	$168.39	9.460%	$184.3197	$184.32	$184.30	$184.30
Purchase #5	$128.98	5.784%	$136.4402	$136.44	$136.45	$136.40
Purchase #6	$28.79	13.465%	$32.6666	$32.67	$32.65	$32.70
Purchase #7	$143.31	3.846%	$148.8217	$148.82	$148.80	$148.80
7 purchase totals =	$694.64		$747.9090	$747.91	$747.85	$747.90