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	$190.36	9.602%	$208.6384	$208.64	$208.65	$208.60
Purchase #2	$123.55	5.616%	$130.4886	$130.49	$130.50	$130.50
Purchase #3	$228.26	4.464%	$238.4495	$238.45	$238.45	$238.40
Purchase #4	$83.75	13.849%	$95.3485	$95.35	$95.35	$95.30
Purchase #5	$127.34	12.874%	$143.7338	$143.73	$143.75	$143.70
Purchase #6	$17.62	6.272%	$18.7251	$18.73	$18.75	$18.70
Purchase #7	$59.30	10.450%	$65.4969	$65.50	$65.50	$65.50
7 purchase totals =	$830.18		$900.8808	$900.89	$900.95	$900.70