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	$46.32	11.667%	$51.7242	$51.72	$51.70	$51.70
Purchase #2	$50.27	9.757%	$55.1748	$55.17	$55.15	$55.20
Purchase #3	$12.29	3.599%	$12.7323	$12.73	$12.75	$12.70
Purchase #4	$40.58	13.211%	$45.941	$45.94	$45.95	$45.90
Purchase #5	$173.57	13.190%	$196.4639	$196.46	$196.45	$196.50
Purchase #6	$24.87	10.442%	$27.4669	$27.47	$27.45	$27.50
Purchase #7	$63.48	7.609%	$68.3102	$68.31	$68.30	$68.30
7 purchase totals =	$411.38		$457.8133	$457.80	$457.75	$457.80