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	$89.51	5.293%	$94.2478	$94.25	$94.25	$94.20
Purchase #2	$109.32	4.202%	$113.9136	$113.91	$113.90	$113.90
Purchase #3	$217.79	7.263%	$233.6081	$233.61	$233.60	$233.60
Purchase #4	$160.74	8.168%	$173.8692	$173.87	$173.85	$173.90
Purchase #5	$111.81	13.613%	$127.0307	$127.03	$127.05	$127.00
Purchase #6	$14.47	9.388%	$15.8284	$15.83	$15.85	$15.80
Purchase #7	$209.82	6.214%	$222.8582	$222.86	$222.85	$222.90
7 purchase totals =	$913.46		$981.3560	$981.36	$981.35	$981.30