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	$205.74	13.354%	$233.2145	$233.21	$233.20	$233.20
Purchase #2	$9.88	11.396%	$11.0059	$11.01	$11.00	$11.00
Purchase #3	$6.36	9.370%	$6.9559	$6.96	$6.95	$7.00
Purchase #4	$91.89	4.339%	$95.8771	$95.88	$95.90	$95.90
Purchase #5	$198.35	3.481%	$205.2546	$205.25	$205.25	$205.30
Purchase #6	$127.68	3.482%	$132.1258	$132.13	$132.15	$132.10
Purchase #7	$52.89	11.847%	$59.1559	$59.16	$59.15	$59.20
7 purchase totals =	$692.79		$743.5897	$743.60	$743.60	$743.70