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	$220.77	11.307%	$245.7325	$245.73	$245.75	$245.70
Purchase #2	$40.57	6.348%	$43.1454	$43.15	$43.15	$43.10
Purchase #3	$117.76	5.191%	$123.8729	$123.87	$123.85	$123.90
Purchase #4	$63.97	10.277%	$70.5442	$70.54	$70.55	$70.50
Purchase #5	$57.65	6.869%	$61.61	$61.61	$61.60	$61.60
Purchase #6	$73.33	12.602%	$82.571	$82.57	$82.55	$82.60
Purchase #7	$97.80	10.856%	$108.4172	$108.42	$108.40	$108.40
7 purchase totals =	$671.85		$735.8932	$735.89	$735.85	$735.80