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	$150.85	11.308%	$167.9081	$167.91	$167.90	$167.90
Purchase #2	$163.54	4.541%	$170.9664	$170.97	$170.95	$171.00
Purchase #3	$163.97	5.213%	$172.5178	$172.52	$172.50	$172.50
Purchase #4	$152.97	3.465%	$158.2704	$158.27	$158.25	$158.30
Purchase #5	$164.47	8.570%	$178.5651	$178.57	$178.55	$178.60
Purchase #6	$33.87	3.524%	$35.0636	$35.06	$35.05	$35.10
Purchase #7	$175.99	8.232%	$190.4775	$190.48	$190.50	$190.50
7 purchase totals =	$1,005.66		$1,073.7689	$1,073.78	$1,073.70	$1,073.90