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	$125.59	4.577%	$131.3383	$131.34	$131.35	$131.30
Purchase #2	$168.81	12.720%	$190.2826	$190.28	$190.30	$190.30
Purchase #3	$187.53	4.607%	$196.1695	$196.17	$196.15	$196.20
Purchase #4	$69.42	9.594%	$76.0802	$76.08	$76.10	$76.10
Purchase #5	$40.39	3.404%	$41.7649	$41.76	$41.75	$41.80
Purchase #6	$41.80	3.651%	$43.3261	$43.33	$43.35	$43.30
Purchase #7	$62.85	5.787%	$66.4871	$66.49	$66.50	$66.50
7 purchase totals =	$696.39		$745.4487	$745.45	$745.50	$745.50