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	$143.92	3.494%	$148.9486	$148.95	$148.95	$148.90
Purchase #2	$143.43	7.723%	$154.5071	$154.51	$154.50	$154.50
Purchase #3	$94.48	6.107%	$100.2499	$100.25	$100.25	$100.20
Purchase #4	$221.30	4.776%	$231.8693	$231.87	$231.85	$231.90
Purchase #5	$104.38	8.147%	$112.8838	$112.88	$112.90	$112.90
Purchase #6	$173.27	9.171%	$189.1606	$189.16	$189.15	$189.20
Purchase #7	$19.95	3.792%	$20.7065	$20.71	$20.70	$20.70
7 purchase totals =	$900.73		$958.3258	$958.33	$958.30	$958.30