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	$132.76	7.615%	$142.8697	$142.87	$142.85	$142.90
Purchase #2	$69.31	11.571%	$77.3299	$77.33	$77.35	$77.30
Purchase #3	$108.37	5.582%	$114.4192	$114.42	$114.40	$114.40
Purchase #4	$107.42	5.817%	$113.6686	$113.67	$113.65	$113.70
Purchase #5	$51.89	5.848%	$54.9245	$54.92	$54.90	$54.90
Purchase #6	$248.98	10.249%	$274.498	$274.50	$274.50	$274.50
Purchase #7	$112.77	12.515%	$126.8832	$126.88	$126.90	$126.90
7 purchase totals =	$831.50		$904.5931	$904.59	$904.55	$904.60