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	$229.28	4.460%	$239.5059	$239.51	$239.50	$239.50
Purchase #2	$52.99	8.380%	$57.4306	$57.43	$57.45	$57.40
Purchase #3	$72.39	13.693%	$82.3024	$82.30	$82.30	$82.30
Purchase #4	$45.95	5.223%	$48.35	$48.35	$48.35	$48.40
Purchase #5	$196.69	8.497%	$213.4027	$213.40	$213.40	$213.40
Purchase #6	$207.92	13.149%	$235.2594	$235.26	$235.25	$235.30
Purchase #7	$133.34	4.459%	$139.2856	$139.29	$139.30	$139.30
7 purchase totals =	$938.56		$1,015.5366	$1,015.54	$1,015.55	$1,015.60