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	$85.41	6.476%	$90.9412	$90.94	$90.95	$90.90
Purchase #2	$27.43	5.657%	$28.9817	$28.98	$29.00	$29.00
Purchase #3	$211.89	4.604%	$221.6454	$221.65	$221.65	$221.60
Purchase #4	$167.50	9.510%	$183.4293	$183.43	$183.45	$183.40
Purchase #5	$178.79	7.671%	$192.505	$192.51	$192.50	$192.50
Purchase #6	$167.64	4.468%	$175.1302	$175.13	$175.15	$175.10
Purchase #7	$113.66	6.119%	$120.6149	$120.61	$120.60	$120.60
7 purchase totals =	$952.32		$1,013.2477	$1,013.25	$1,013.30	$1,013.10