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	$149.93	4.470%	$156.6319	$156.63	$156.65	$156.60
Purchase #2	$168.92	9.560%	$185.0688	$185.07	$185.05	$185.10
Purchase #3	$71.84	9.675%	$78.7905	$78.79	$78.80	$78.80
Purchase #4	$250.64	8.863%	$272.8542	$272.85	$272.85	$272.90
Purchase #5	$208.55	3.712%	$216.2914	$216.29	$216.30	$216.30
Purchase #6	$84.33	11.514%	$94.0398	$94.04	$94.05	$94.00
Purchase #7	$92.55	11.717%	$103.3941	$103.39	$103.40	$103.40
7 purchase totals =	$1,026.76		$1,107.0707	$1,107.06	$1,107.10	$1,107.10