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	$202.28	13.189%	$228.9587	$228.96	$228.95	$229.00
Purchase #2	$98.48	10.321%	$108.6441	$108.64	$108.65	$108.60
Purchase #3	$111.98	13.820%	$127.4556	$127.46	$127.45	$127.50
Purchase #4	$209.97	11.839%	$234.8283	$234.83	$234.85	$234.80
Purchase #5	$187.93	3.542%	$194.5865	$194.59	$194.60	$194.60
Purchase #6	$12.83	7.428%	$13.783	$13.78	$13.80	$13.80
Purchase #7	$125.43	12.860%	$141.5603	$141.56	$141.55	$141.60
7 purchase totals =	$948.90		$1,049.8165	$1,049.82	$1,049.85	$1,049.90