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	$90.51	3.321%	$93.5158	$93.52	$93.50	$93.50
Purchase #2	$196.83	12.519%	$221.4711	$221.47	$221.45	$221.50
Purchase #3	$78.89	5.606%	$83.3126	$83.31	$83.30	$83.30
Purchase #4	$161.52	13.863%	$183.9115	$183.91	$183.90	$183.90
Purchase #5	$127.82	3.289%	$132.024	$132.02	$132.00	$132.00
Purchase #6	$198.31	10.838%	$219.8028	$219.80	$219.80	$219.80
Purchase #7	$91.27	12.330%	$102.5236	$102.52	$102.50	$102.50
7 purchase totals =	$945.15		$1,036.5614	$1,036.55	$1,036.45	$1,036.50