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	$179.74	9.177%	$196.2347	$196.23	$196.25	$196.20
Purchase #2	$77.38	13.324%	$87.6901	$87.69	$87.70	$87.70
Purchase #3	$33.34	3.799%	$34.6066	$34.61	$34.60	$34.60
Purchase #4	$135.35	3.542%	$140.1441	$140.14	$140.15	$140.10
Purchase #5	$193.70	11.816%	$216.5876	$216.59	$216.60	$216.60
Purchase #6	$103.35	7.540%	$111.1426	$111.14	$111.15	$111.10
Purchase #7	$237.34	4.522%	$248.0725	$248.07	$248.05	$248.10
7 purchase totals =	$960.20		$1,034.4782	$1,034.47	$1,034.50	$1,034.40