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	$114.41	3.499%	$118.4132	$118.41	$118.40	$118.40
Purchase #2	$76.27	4.108%	$79.4032	$79.40	$79.40	$79.40
Purchase #3	$29.32	13.179%	$33.1841	$33.18	$33.20	$33.20
Purchase #4	$98.59	11.285%	$109.7159	$109.72	$109.70	$109.70
Purchase #5	$44.47	12.160%	$49.8776	$49.88	$49.90	$49.90
Purchase #6	$10.49	9.598%	$11.4968	$11.50	$11.50	$11.50
Purchase #7	$149.27	6.762%	$159.3636	$159.36	$159.35	$159.40
7 purchase totals =	$522.82		$561.4544	$561.45	$561.45	$561.50