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	$175.42	5.507%	$185.0804	$185.08	$185.10	$185.10
Purchase #2	$10.85	12.540%	$12.2106	$12.21	$12.20	$12.20
Purchase #3	$228.94	9.419%	$250.5039	$250.50	$250.50	$250.50
Purchase #4	$117.37	9.811%	$128.8852	$128.89	$128.90	$128.90
Purchase #5	$227.33	12.606%	$255.9872	$255.99	$256.00	$256.00
Purchase #6	$233.63	13.391%	$264.9154	$264.92	$264.90	$264.90
Purchase #7	$107.92	6.466%	$114.8981	$114.90	$114.90	$114.90
7 purchase totals =	$1,101.46		$1,212.4808	$1,212.49	$1,212.50	$1,212.50