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	$243.40	8.286%	$263.5681	$263.57	$263.55	$263.60
Purchase #2	$127.88	3.698%	$132.609	$132.61	$132.60	$132.60
Purchase #3	$170.83	6.506%	$181.9442	$181.94	$181.95	$181.90
Purchase #4	$28.96	13.785%	$32.9521	$32.95	$32.95	$33.00
Purchase #5	$244.73	6.653%	$261.0119	$261.01	$261.00	$261.00
Purchase #6	$101.89	6.557%	$108.5709	$108.57	$108.55	$108.60
Purchase #7	$85.87	6.543%	$91.4885	$91.49	$91.50	$91.50
7 purchase totals =	$1,003.56		$1,072.1447	$1,072.14	$1,072.10	$1,072.20