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	$70.99	3.870%	$73.7373	$73.74	$73.75	$73.70
Purchase #2	$53.81	9.721%	$59.0409	$59.04	$59.05	$59.00
Purchase #3	$11.48	7.381%	$12.3273	$12.33	$12.35	$12.30
Purchase #4	$127.88	11.329%	$142.3675	$142.37	$142.35	$142.40
Purchase #5	$196.95	4.581%	$205.9723	$205.97	$205.95	$206.00
Purchase #6	$136.30	12.635%	$153.5215	$153.52	$153.50	$153.50
Purchase #7	$107.27	4.712%	$112.3246	$112.32	$112.30	$112.30
7 purchase totals =	$704.68		$759.2914	$759.29	$759.25	$759.20