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	$83.27	11.613%	$92.9401	$92.94	$92.95	$92.90
Purchase #2	$86.96	4.285%	$90.6862	$90.69	$90.70	$90.70
Purchase #3	$61.86	6.235%	$65.717	$65.72	$65.70	$65.70
Purchase #4	$152.48	9.475%	$166.9275	$166.93	$166.95	$166.90
Purchase #5	$35.75	11.348%	$39.8069	$39.81	$39.80	$39.80
Purchase #6	$54.47	3.757%	$56.5164	$56.52	$56.50	$56.50
Purchase #7	$37.56	11.864%	$42.0161	$42.02	$42.00	$42.00
7 purchase totals =	$512.35		$554.6102	$554.63	$554.60	$554.50