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	$11.50	5.545%	$12.1377	$12.14	$12.15	$12.10
Purchase #2	$89.77	6.804%	$95.878	$95.88	$95.90	$95.90
Purchase #3	$114.25	4.797%	$119.7306	$119.73	$119.75	$119.70
Purchase #4	$7.29	8.175%	$7.886	$7.89	$7.90	$7.90
Purchase #5	$10.83	5.366%	$11.4111	$11.41	$11.40	$11.40
Purchase #6	$141.91	11.811%	$158.671	$158.67	$158.65	$158.70
Purchase #7	$47.54	13.218%	$53.8238	$53.82	$53.80	$53.80
7 purchase totals =	$423.09		$459.5382	$459.54	$459.55	$459.50