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	$247.85	6.479%	$263.9082	$263.91	$263.90	$263.90
Purchase #2	$28.91	5.524%	$30.507	$30.51	$30.50	$30.50
Purchase #3	$15.59	12.342%	$17.5141	$17.51	$17.50	$17.50
Purchase #4	$31.26	5.208%	$32.888	$32.89	$32.90	$32.90
Purchase #5	$143.57	5.560%	$151.5525	$151.55	$151.55	$151.60
Purchase #6	$171.55	12.422%	$192.8599	$192.86	$192.85	$192.90
Purchase #7	$18.45	5.641%	$19.4908	$19.49	$19.50	$19.50
7 purchase totals =	$657.18		$708.7205	$708.72	$708.70	$708.80