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	$114.91	12.540%	$129.3197	$129.32	$129.30	$129.30
Purchase #2	$9.82	13.601%	$11.1556	$11.16	$11.15	$11.20
Purchase #3	$185.67	6.378%	$197.512	$197.51	$197.50	$197.50
Purchase #4	$72.44	13.860%	$82.4802	$82.48	$82.50	$82.50
Purchase #5	$242.66	13.565%	$275.5768	$275.58	$275.60	$275.60
Purchase #6	$153.55	7.143%	$164.5181	$164.52	$164.50	$164.50
Purchase #7	$216.83	6.495%	$230.9131	$230.91	$230.90	$230.90
7 purchase totals =	$995.88		$1,091.4755	$1,091.48	$1,091.45	$1,091.50