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	$103.66	13.371%	$117.5204	$117.52	$117.50	$117.50
Purchase #2	$47.43	13.349%	$53.7614	$53.76	$53.75	$53.80
Purchase #3	$135.38	4.840%	$141.9324	$141.93	$141.95	$141.90
Purchase #4	$50.51	7.732%	$54.4154	$54.42	$54.40	$54.40
Purchase #5	$92.85	5.606%	$98.0552	$98.06	$98.05	$98.10
Purchase #6	$20.62	5.197%	$21.6916	$21.69	$21.70	$21.70
Purchase #7	$227.88	9.467%	$249.4534	$249.45	$249.45	$249.50
7 purchase totals =	$678.33		$736.8298	$736.83	$736.80	$736.90