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	$59.52	13.528%	$67.5719	$67.57	$67.55	$67.60
Purchase #2	$63.72	4.401%	$66.5243	$66.52	$66.50	$66.50
Purchase #3	$180.81	13.304%	$204.865	$204.87	$204.85	$204.90
Purchase #4	$234.83	3.472%	$242.9833	$242.98	$243.00	$243.00
Purchase #5	$65.80	9.277%	$71.9043	$71.90	$71.90	$71.90
Purchase #6	$247.26	5.262%	$260.2708	$260.27	$260.25	$260.30
Purchase #7	$87.74	13.629%	$99.6981	$99.70	$99.70	$99.70
7 purchase totals =	$939.68		$1,013.8177	$1,013.81	$1,013.75	$1,013.90