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	$148.50	3.647%	$153.9158	$153.92	$153.90	$153.90
Purchase #2	$123.27	6.683%	$131.5081	$131.51	$131.50	$131.50
Purchase #3	$53.55	11.804%	$59.871	$59.87	$59.85	$59.90
Purchase #4	$9.47	3.391%	$9.7911	$9.79	$9.80	$9.80
Purchase #5	$72.54	12.443%	$81.5662	$81.57	$81.55	$81.60
Purchase #6	$27.55	13.866%	$31.3701	$31.37	$31.35	$31.40
Purchase #7	$242.94	10.584%	$268.6528	$268.65	$268.65	$268.70
7 purchase totals =	$677.82		$736.6751	$736.68	$736.60	$736.80