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	$70.27	4.714%	$73.5825	$73.58	$73.60	$73.60
Purchase #2	$235.84	9.564%	$258.3957	$258.40	$258.40	$258.40
Purchase #3	$98.29	11.178%	$109.2769	$109.28	$109.30	$109.30
Purchase #4	$35.68	13.693%	$40.5657	$40.57	$40.55	$40.60
Purchase #5	$102.55	5.697%	$108.3923	$108.39	$108.40	$108.40
Purchase #6	$187.93	13.705%	$213.6858	$213.69	$213.70	$213.70
Purchase #7	$242.30	6.340%	$257.6618	$257.66	$257.65	$257.70
7 purchase totals =	$972.86		$1,061.5607	$1,061.57	$1,061.60	$1,061.70