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	$177.80	4.498%	$185.7974	$185.80	$185.80	$185.80
Purchase #2	$51.84	5.863%	$54.8794	$54.88	$54.90	$54.90
Purchase #3	$127.83	11.297%	$142.271	$142.27	$142.25	$142.30
Purchase #4	$217.44	11.124%	$241.628	$241.63	$241.65	$241.60
Purchase #5	$69.93	4.186%	$72.8573	$72.86	$72.85	$72.90
Purchase #6	$126.66	13.199%	$143.3779	$143.38	$143.40	$143.40
Purchase #7	$203.89	3.522%	$211.071	$211.07	$211.05	$211.10
7 purchase totals =	$975.39		$1,051.8820	$1,051.89	$1,051.90	$1,052.00