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	$57.37	3.177%	$59.1926	$59.19	$59.20	$59.20
Purchase #2	$140.37	8.236%	$151.9309	$151.93	$151.95	$151.90
Purchase #3	$39.90	13.109%	$45.1305	$45.13	$45.15	$45.10
Purchase #4	$53.65	11.624%	$59.8863	$59.89	$59.90	$59.90
Purchase #5	$61.71	7.411%	$66.2833	$66.28	$66.30	$66.30
Purchase #6	$194.50	11.769%	$217.3907	$217.39	$217.40	$217.40
Purchase #7	$177.89	8.242%	$192.5517	$192.55	$192.55	$192.60
7 purchase totals =	$725.39		$792.3660	$792.36	$792.45	$792.40