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	$230.91	10.526%	$255.2156	$255.22	$255.20	$255.20
Purchase #2	$32.30	10.179%	$35.5878	$35.59	$35.60	$35.60
Purchase #3	$196.56	4.482%	$205.3698	$205.37	$205.35	$205.40
Purchase #4	$127.74	4.337%	$133.2801	$133.28	$133.30	$133.30
Purchase #5	$126.77	10.671%	$140.2976	$140.30	$140.30	$140.30
Purchase #6	$211.92	4.555%	$221.573	$221.57	$221.55	$221.60
Purchase #7	$36.93	4.360%	$38.5401	$38.54	$38.55	$38.50
7 purchase totals =	$963.13		$1,029.8640	$1,029.87	$1,029.85	$1,029.90