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	$227.51	8.764%	$247.449	$247.45	$247.45	$247.40
Purchase #2	$34.50	3.146%	$35.5854	$35.59	$35.60	$35.60
Purchase #3	$178.85	11.210%	$198.8991	$198.90	$198.90	$198.90
Purchase #4	$11.88	13.136%	$13.4406	$13.44	$13.45	$13.40
Purchase #5	$189.59	5.654%	$200.3094	$200.31	$200.30	$200.30
Purchase #6	$10.56	11.606%	$11.7856	$11.79	$11.80	$11.80
Purchase #7	$172.83	9.392%	$189.0622	$189.06	$189.05	$189.10
7 purchase totals =	$825.72		$896.5313	$896.54	$896.55	$896.50