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	$38.44	7.665%	$41.3864	$41.39	$41.40	$41.40
Purchase #2	$63.65	12.255%	$71.4503	$71.45	$71.45	$71.50
Purchase #3	$153.54	7.836%	$165.5714	$165.57	$165.55	$165.60
Purchase #4	$103.27	9.243%	$112.8152	$112.82	$112.80	$112.80
Purchase #5	$46.26	12.176%	$51.8926	$51.89	$51.90	$51.90
Purchase #6	$184.47	4.458%	$192.6937	$192.69	$192.70	$192.70
Purchase #7	$241.69	9.560%	$264.7956	$264.80	$264.80	$264.80
7 purchase totals =	$831.32		$900.6052	$900.61	$900.60	$900.70