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	$100.71	4.576%	$105.3185	$105.32	$105.30	$105.30
Purchase #2	$61.56	10.271%	$67.8828	$67.88	$67.90	$67.90
Purchase #3	$52.25	8.513%	$56.698	$56.70	$56.70	$56.70
Purchase #4	$149.60	4.482%	$156.3051	$156.31	$156.30	$156.30
Purchase #5	$64.40	5.132%	$67.705	$67.71	$67.70	$67.70
Purchase #6	$133.76	3.209%	$138.0524	$138.05	$138.05	$138.10
Purchase #7	$70.36	7.257%	$75.466	$75.47	$75.45	$75.50
7 purchase totals =	$632.64		$667.4278	$667.44	$667.40	$667.50