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	$61.67	8.632%	$66.9934	$66.99	$67.00	$67.00
Purchase #2	$81.76	9.634%	$89.6368	$89.64	$89.65	$89.60
Purchase #3	$140.27	8.281%	$151.8858	$151.89	$151.90	$151.90
Purchase #4	$10.50	8.385%	$11.3804	$11.38	$11.40	$11.40
Purchase #5	$78.43	5.867%	$83.0315	$83.03	$83.05	$83.00
Purchase #6	$30.27	7.494%	$32.5384	$32.54	$32.55	$32.50
Purchase #7	$131.45	5.450%	$138.614	$138.61	$138.60	$138.60
7 purchase totals =	$534.35		$574.0803	$574.08	$574.15	$574.00