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	$185.78	10.271%	$204.8615	$204.86	$204.85	$204.90
Purchase #2	$219.94	5.514%	$232.0675	$232.07	$232.05	$232.10
Purchase #3	$236.67	3.110%	$244.0304	$244.03	$244.05	$244.00
Purchase #4	$64.31	12.118%	$72.1031	$72.10	$72.10	$72.10
Purchase #5	$121.61	5.797%	$128.6597	$128.66	$128.65	$128.70
Purchase #6	$107.31	4.469%	$112.1057	$112.11	$112.10	$112.10
Purchase #7	$66.30	9.505%	$72.6018	$72.60	$72.60	$72.60
7 purchase totals =	$1,001.92		$1,066.4297	$1,066.43	$1,066.40	$1,066.50