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	$245.64	4.404%	$256.458	$256.46	$256.45	$256.50
Purchase #2	$221.41	10.358%	$244.3436	$244.34	$244.35	$244.30
Purchase #3	$55.82	10.353%	$61.599	$61.60	$61.60	$61.60
Purchase #4	$71.93	9.256%	$78.5878	$78.59	$78.60	$78.60
Purchase #5	$47.26	12.692%	$53.2582	$53.26	$53.25	$53.30
Purchase #6	$245.99	4.356%	$256.7053	$256.71	$256.70	$256.70
Purchase #7	$125.81	11.144%	$139.8303	$139.83	$139.85	$139.80
7 purchase totals =	$1,013.86		$1,090.7822	$1,090.79	$1,090.80	$1,090.80