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	$145.32	13.838%	$165.4294	$165.43	$165.45	$165.40
Purchase #2	$127.51	3.609%	$132.1118	$132.11	$132.10	$132.10
Purchase #3	$143.62	8.564%	$155.9196	$155.92	$155.90	$155.90
Purchase #4	$95.77	7.654%	$103.1002	$103.10	$103.10	$103.10
Purchase #5	$103.84	8.749%	$112.925	$112.93	$112.95	$112.90
Purchase #6	$80.81	6.529%	$86.0861	$86.09	$86.10	$86.10
Purchase #7	$56.90	3.489%	$58.8852	$58.89	$58.90	$58.90
7 purchase totals =	$753.77		$814.4573	$814.47	$814.50	$814.40