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	$29.89	13.207%	$33.8376	$33.84	$33.85	$33.80
Purchase #2	$70.48	11.652%	$78.6923	$78.69	$78.70	$78.70
Purchase #3	$35.40	9.613%	$38.803	$38.80	$38.80	$38.80
Purchase #4	$112.79	11.349%	$125.5905	$125.59	$125.60	$125.60
Purchase #5	$39.74	6.397%	$42.2822	$42.28	$42.30	$42.30
Purchase #6	$56.94	9.514%	$62.3573	$62.36	$62.35	$62.40
Purchase #7	$50.93	5.723%	$53.8447	$53.84	$53.85	$53.80
7 purchase totals =	$396.17		$435.4076	$435.40	$435.45	$435.40