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	$124.85	5.668%	$131.9265	$131.93	$131.95	$131.90
Purchase #2	$40.52	3.167%	$41.8033	$41.80	$41.80	$41.80
Purchase #3	$146.98	9.475%	$160.9064	$160.91	$160.90	$160.90
Purchase #4	$127.80	8.496%	$138.6579	$138.66	$138.65	$138.70
Purchase #5	$138.78	4.682%	$145.2777	$145.28	$145.30	$145.30
Purchase #6	$167.60	7.322%	$179.8717	$179.87	$179.85	$179.90
Purchase #7	$97.54	4.449%	$101.8796	$101.88	$101.90	$101.90
7 purchase totals =	$844.07		$900.3231	$900.33	$900.35	$900.40