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	$179.70	11.613%	$200.5686	$200.57	$200.55	$200.60
Purchase #2	$226.38	3.166%	$233.5472	$233.55	$233.55	$233.50
Purchase #3	$136.88	5.630%	$144.5863	$144.59	$144.60	$144.60
Purchase #4	$205.71	11.126%	$228.5973	$228.60	$228.60	$228.60
Purchase #5	$157.43	6.571%	$167.7747	$167.77	$167.75	$167.80
Purchase #6	$139.87	6.263%	$148.6301	$148.63	$148.65	$148.60
Purchase #7	$239.45	6.103%	$254.0636	$254.06	$254.05	$254.10
7 purchase totals =	$1,285.42		$1,377.7678	$1,377.77	$1,377.75	$1,377.80