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	$126.64	7.716%	$136.4115	$136.41	$136.40	$136.40
Purchase #2	$15.87	10.709%	$17.5695	$17.57	$17.55	$17.60
Purchase #3	$47.53	5.148%	$49.9768	$49.98	$50.00	$50.00
Purchase #4	$17.61	5.242%	$18.5331	$18.53	$18.55	$18.50
Purchase #5	$47.32	12.837%	$53.3945	$53.39	$53.40	$53.40
Purchase #6	$43.58	4.360%	$45.4801	$45.48	$45.50	$45.50
Purchase #7	$65.86	11.665%	$73.5426	$73.54	$73.55	$73.50
7 purchase totals =	$364.41		$394.9081	$394.90	$394.95	$394.90