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	$94.99	5.383%	$100.1033	$100.10	$100.10	$100.10
Purchase #2	$24.71	13.733%	$28.1034	$28.10	$28.10	$28.10
Purchase #3	$149.90	3.343%	$154.9112	$154.91	$154.90	$154.90
Purchase #4	$227.65	4.508%	$237.9125	$237.91	$237.90	$237.90
Purchase #5	$146.78	12.263%	$164.7796	$164.78	$164.80	$164.80
Purchase #6	$208.92	3.350%	$215.9188	$215.92	$215.90	$215.90
Purchase #7	$137.94	10.667%	$152.6541	$152.65	$152.65	$152.70
7 purchase totals =	$990.89		$1,054.3829	$1,054.37	$1,054.35	$1,054.40