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	$83.73	3.841%	$86.9461	$86.95	$86.95	$86.90
Purchase #2	$164.78	6.561%	$175.5912	$175.59	$175.60	$175.60
Purchase #3	$47.78	11.137%	$53.1013	$53.10	$53.10	$53.10
Purchase #4	$28.37	4.713%	$29.7071	$29.71	$29.70	$29.70
Purchase #5	$74.94	13.552%	$85.0959	$85.10	$85.10	$85.10
Purchase #6	$31.62	8.171%	$34.2037	$34.20	$34.20	$34.20
Purchase #7	$119.83	6.531%	$127.6561	$127.66	$127.65	$127.70
7 purchase totals =	$551.05		$592.3014	$592.31	$592.30	$592.30