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	$42.83	13.593%	$48.6519	$48.65	$48.65	$48.70
Purchase #2	$234.88	11.690%	$262.3375	$262.34	$262.35	$262.30
Purchase #3	$83.38	3.868%	$86.6051	$86.61	$86.60	$86.60
Purchase #4	$113.78	12.359%	$127.8421	$127.84	$127.85	$127.80
Purchase #5	$144.68	4.291%	$150.8882	$150.89	$150.90	$150.90
Purchase #6	$248.35	6.135%	$263.5863	$263.59	$263.60	$263.60
Purchase #7	$174.73	8.463%	$189.5174	$189.52	$189.50	$189.50
7 purchase totals =	$1,042.63		$1,129.4285	$1,129.44	$1,129.45	$1,129.40