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	$150.69	11.665%	$168.268	$168.27	$168.25	$168.30
Purchase #2	$41.82	3.343%	$43.218	$43.22	$43.20	$43.20
Purchase #3	$30.86	9.475%	$33.784	$33.78	$33.80	$33.80
Purchase #4	$149.40	7.150%	$160.0821	$160.08	$160.10	$160.10
Purchase #5	$7.33	11.131%	$8.1459	$8.15	$8.15	$8.10
Purchase #6	$230.50	13.105%	$260.707	$260.71	$260.70	$260.70
Purchase #7	$234.29	8.526%	$254.2656	$254.27	$254.25	$254.30
7 purchase totals =	$844.89		$928.4706	$928.48	$928.45	$928.50