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	$154.45	3.537%	$159.9129	$159.91	$159.90	$159.90
Purchase #2	$172.59	5.687%	$182.4052	$182.41	$182.40	$182.40
Purchase #3	$112.49	10.614%	$124.4297	$124.43	$124.45	$124.40
Purchase #4	$248.27	4.140%	$258.5484	$258.55	$258.55	$258.50
Purchase #5	$77.40	11.230%	$86.092	$86.09	$86.10	$86.10
Purchase #6	$250.66	13.257%	$283.89	$283.89	$283.90	$283.90
Purchase #7	$39.29	10.391%	$43.3726	$43.37	$43.35	$43.40
7 purchase totals =	$1,055.15		$1,138.6508	$1,138.65	$1,138.65	$1,138.60