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	$57.41	3.473%	$59.4038	$59.40	$59.40	$59.40
Purchase #2	$126.87	3.826%	$131.724	$131.72	$131.70	$131.70
Purchase #3	$12.26	13.324%	$13.8935	$13.89	$13.90	$13.90
Purchase #4	$229.40	3.686%	$237.8557	$237.86	$237.85	$237.90
Purchase #5	$204.33	11.389%	$227.6011	$227.60	$227.60	$227.60
Purchase #6	$108.59	13.584%	$123.3409	$123.34	$123.35	$123.30
Purchase #7	$211.50	11.487%	$235.795	$235.80	$235.80	$235.80
7 purchase totals =	$950.36		$1,029.6140	$1,029.61	$1,029.60	$1,029.60