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	$235.50	11.119%	$261.6852	$261.69	$261.70	$261.70
Purchase #2	$210.66	13.737%	$239.5984	$239.60	$239.60	$239.60
Purchase #3	$79.96	7.358%	$85.8435	$85.84	$85.85	$85.80
Purchase #4	$32.46	10.722%	$35.9404	$35.94	$35.95	$35.90
Purchase #5	$32.87	13.693%	$37.3709	$37.37	$37.35	$37.40
Purchase #6	$110.73	11.606%	$123.5813	$123.58	$123.60	$123.60
Purchase #7	$133.64	13.748%	$152.0128	$152.01	$152.00	$152.00
7 purchase totals =	$835.82		$936.0325	$936.03	$936.05	$936.00