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	$28.27	3.765%	$29.3344	$29.33	$29.35	$29.30
Purchase #2	$241.84	6.635%	$257.8861	$257.89	$257.90	$257.90
Purchase #3	$14.70	11.873%	$16.4453	$16.45	$16.45	$16.40
Purchase #4	$182.97	9.275%	$199.9405	$199.94	$199.95	$199.90
Purchase #5	$146.29	13.165%	$165.5491	$165.55	$165.55	$165.50
Purchase #6	$143.61	5.258%	$151.161	$151.16	$151.15	$151.20
Purchase #7	$174.85	12.486%	$196.6818	$196.68	$196.70	$196.70
7 purchase totals =	$932.53		$1,016.9982	$1,017.00	$1,017.05	$1,016.90