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	$53.56	11.154%	$59.5341	$59.53	$59.55	$59.50
Purchase #2	$100.69	8.747%	$109.4974	$109.50	$109.50	$109.50
Purchase #3	$158.57	8.572%	$172.1626	$172.16	$172.15	$172.20
Purchase #4	$23.50	4.569%	$24.5737	$24.57	$24.55	$24.60
Purchase #5	$202.64	4.427%	$211.6109	$211.61	$211.60	$211.60
Purchase #6	$71.35	4.253%	$74.3845	$74.38	$74.40	$74.40
Purchase #7	$93.65	9.436%	$102.4868	$102.49	$102.50	$102.50
7 purchase totals =	$703.96		$754.2500	$754.24	$754.25	$754.30