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	$138.38	3.437%	$143.1361	$143.14	$143.15	$143.10
Purchase #2	$196.26	13.521%	$222.7963	$222.80	$222.80	$222.80
Purchase #3	$149.73	6.155%	$158.9459	$158.95	$158.95	$158.90
Purchase #4	$85.90	11.611%	$95.8738	$95.87	$95.85	$95.90
Purchase #5	$222.68	9.114%	$242.9751	$242.98	$243.00	$243.00
Purchase #6	$52.69	13.696%	$59.9064	$59.91	$59.90	$59.90
Purchase #7	$101.68	11.120%	$112.9868	$112.99	$113.00	$113.00
7 purchase totals =	$947.32		$1,036.6204	$1,036.64	$1,036.65	$1,036.60